Effect of BPAI claim construction in litigation

In an earlier post (here), I discussed the BPAI Ex Parte Jenkins decision, in which the Board construed the claimed "storage space" to be bigger than a rivet, given the teachings of Applicant's spec.

Would the Applicant have a hard time arguing in litigation that an accused product with a tiny storage space infringes? What about a storage space big enough to hold a couple of fishing flies? That's bigger than a rivet, but not by much.

Or is the Board's construction irrelevant in litigation? If so, why? Can't you say that the size of the storage space was what distinguished over the reference, so a sort of prosecution history estoppel applies, even though it was the Board that made the distinction? Or is the estoppel doctrine not relevant unless the Applicant argued the size of the storage space was a patentable distinction?

I don't know the answer to these questions. I'm just thinking out loud.

Res judicata in a rejection

If you get an adverse decision from the BPAI, you can continue prosecution by filing an RCE with claim amendments and/or new evidence. I came across an application (Appl. No. 10/023,117) in which the Applicant did this, and the Examiner invoked res judicata to reject a claim, even though amendments were made.

Although I've never come across res judicata in patent prosecution, the MPEP specifically provides for it in section 706.03(w). It does make sense to me that once the Board has affirmed a claim rejection, that rejection can be applied again with no further explanation because the issue has already been decided.

What struck me as strange is that the Applicant had amended the claims. But the Examiner took the position that the amended claim was not patentably distinct from the claim presented at appeal:

The sole change to claim 6 is changing the final clause from "outputting ... to a destination identified in the ... instruction" to "outputting ... to a destination register identified in the ... instruction". As it was shown in the examiner's answer to appeal mailed November 14, 2007 that Abbott output to a destination register, the claim is not patentably distinct from that affirmed by the Board of Patent Appeals and Interferences.

I think it's clear that "destination register" has different scope than "destination," such that the Examiner must make a new finding in the post-RCE Office Action that the reference discloses the added feature. Certainly it's not enough that the Examiner's Answer "shows" that the reference teaches the amended feature, because a statement in an Examiner's Answer is an allegation, not a judicially established fact.

In fact, I think the Board's decision implied that the claim on appeal ("outputting to a destination) was patentably distinguishable from the claim in the RCE ("outputting to a destination register"). This happened when the Board pointed out that the Applicant was arguing about a feature which was not present in the claim on appeal:

Initially, we note that although Appellants argue that Abbott does not teach that the output of the transposition circuit 410 is provided to a destination register that is specified in an instruction ... the Appellants have chosen to draft the claims, claim 1 in particular, far more broadly.

By pointing out that the claim on appeal did not specify "destination register", I think the Board in effect said that a claim without this feature is patentably distinct from a claim with this feature. Thus, res judicata does not apply to the amended claim.

I should note that the Examiner did not solely rely on res judicata. As recommended by the MPEP, a prior art rejection which was applied also, in this case, the same rejection which was appealed was "maintained and incorporated by reference."

"Portable" means "removable" (Ex parte Fabritius)

Ex parte Fabritius
(Appeal 2008-0068; Appl. No. 10/449,707; Tech. Center 2100)
Decided: May 29, 2008

The claim at issue was to a "method for handling data in a fixed memory associated with a portable electronic communication device ... and an operation of storing data in said fixed memory comprises ..."

The reference disclosed an automobile radar system. The Applicant argued that the system was not a "portable communication electronic device." The Board first found that this phrase in the preamble was not limiting. The Board should have stopped there, because the only other Applicant argument was "non-analogous art," which the Board noted was irrelevant for anticipation.

But the Board continued on, and shot itself in the foot. Here is the Board's strained reasoning as to why the automobile radar system was "portable":

At least a portion of the communication device described by Woll is removable, and thus “portable” within some meaning urged by Appellants. RAM card 20 (Woll Fig. 2) may be removed from the system so that the data may be read by a personal computer 60 (Fig. 6).

What's going on here? Did the Board confused "movable" with "removable"? I can see that "movable" is a synonym for "portable", but not "removable". Also, even if there is some overlap between removable and portable, why is the entire thing portable simply because a portion of it is removable? Is my house portable because the door is removable?

Claimed "storage space" evaluated relative to the preamble (Ex parte Jenkins)

Ex parte Jenkins
(Appeal 2009005028, Appl. No. 11/204,671, Tech. Center 3600)
Decided September 30, 2009

I don't deal with a lot of mechanical cases, though I do read a fair number of BPAI decisions for Technology Center 3600. The claim in this mechanical case was for "a carrying case for transporting a user's fishing equipment". The Board actually limited the broadest reasonable interpretation to the broadest reasonable in view of the specification.

Fraser does not teach a storage space as claimed. Although Appellant’s claim 1 does not include express limitations on the size or dimensions of the storage space claimed, Appellant’s specification explains that the storage space is provided for holding fishing tackle and knives (FF 4). The claims are directed to “[a] carrying case for transporting a user's fishing equipment.” In the context of Appellant’s specification and claims (which are part of the specification, see Merck & Co., Inc. v. Teva Pharm. USA, Inc., 347 F.3d 1367, 1371 (Fed. Cir. 2003)), it is not reasonable to construe “storage space” as including a space defined by the thickness of a rivet head. Thus, though Fraser teaches an external container and an insert for holding fishing rods, it does not anticipate the claimed carrying case because it does not teach a storage space.

I know there's a fine line between importing limitations from the spec into the claims, and perhaps this one crossed that line. Perhaps the Applicant should have put "the storage space sized to fit fishing equipment" as an explicit limitation. (Would this have had the intended limiting effect?)

That said, it was refreshing to see the Board pay attention to the second half of the BRI standard: broadest reasonable interpretation in view of the spec. Of the BPAI decisions I read, I feel that a significant number use a claim construction that does not meet this standard.

This was a case in which the Applicant won the battle but lost the war. The Board reversed the Examiner's §102 rejection based on this claim construction, but went on to find an appropriate-sized space in another reference, and so entered a §103 rejection.

Explanation of Examiner incentives

I've alluded to the Examiner count system a couple of times on this blog, but never bothered to explain it. I found a series of posts on the Patents 101 blog, titled "What is the Examiner's Motivation?", which has a good overview of the Examiner performance evaluation system. If you don't know much about counts and biweeks at the PTO, I think this would be good reading.

The posts are written by a patent attorney, and I'm not sure I agree with all the conclusions he draws about how the count system plays out. Nonetheless, I'm always interested in hearing different viewpoints, so these posts are worth reading for that reason too.

Implicit teachings of a reference

When arguing that a reference doesn't teach, some practitioners focus exclusively on the explicit or literal teachings of the reference, and ignore what a POSITA would understand the reference to teach implicitly. There are some good reasons for doing this — prosecution history estoppel and the danger of mischaracterizing the reference come to mind. But be aware that MPEP 2144.01 states that the Examiner is allowed to use implicit teachings too:

[I]n considering the disclosure of a reference, it is proper to take into account not only specific teachings of the reference but also the inferences which one skilled in the art would reasonably be expected to draw therefrom.
In re Preda, 401 F.2d 825, 826, 159 USPQ 342, 344 (CCPA 1968).

Sometimes reading between the lines means simply recognizing that a reference is using a different term than the one that appears in the claim. Other times, it means putting together several explicit teachings to draw an inference. And sometimes it means recognizing that the absence of a teaching is evidence that something wasn't important enough to discuss rather than evidence that it wasn't known.

Here are a few instances where the BPAI affirmed a rejection based on implicit teachings.

Ex parte Nawathe: "While Lee's system specifically discloses loading data for a single XML document into the relational database, it is not necessarily so limited. In other words, the ordinarily skilled artisan would have recognized that loading multiple XML documents in a relational database to be within the purview of the prior art as evidenced by Lee's disclosure that metadata is generally known to describe information about more than one of such documents."

Ex parte Symbol Technologies, Inc.: "All that is required by these claims is that the keys be capable of being individually engaged by the thumb or fingers of the hand holding the housing ... As articulated by the Examiner, the size of Gombrich's pocket terminal is sufficiently small to allow users to hold the pocket terminal in the user's palm and reach the keys with their thumb without pressing other keys. We find that one of ordinary skill in the art reasonably would infer that the keys of Gombrich are capable of being individually engaged by the thumb of the hand holding the housing in view of the specifically disclosed dimensions of the pocket terminal and the teachings in Gombrich that the pocket terminal is 'pocket-sized', 'portable' and allows for 'one handed' operation.”

Ex parte Zybura: "We find that the ordinarily skilled artisan would have readily recognized that Thatcher's disclosure of inconsistencies that arise between the replicas of a namespace due to the propagation delay in the updates teaches or suggests the claimed determination that modification to a namespace results in conflicting information between the replicas. Similarly, we find that Thatcher's disclosure of all the replicas having identical objects at the end of the update teaches the claimed removal of the identified conflict before the update takes place in the second namespace."

Ex parte McCormack: "We find that Jiang's storage of device preferences and service preferences teaches storing the claimed digital identity for a wireless user device. While Jiang does not particularly disclose the user device to be a DTV, it suggests that the WPM would provide seamless access to information without regard to the type of device available to the user. In other words, the ordinarily skilled artisan would readily appreciate that regardless of the type of device available to the user, the WPM's database or repository would still store digital entity or preference data for whatever device that it identifies."

Update on Web Pages as Non-Patent Prior Art

Earlier I posted (here) about the use of web pages as prior art. Typically, the Examiner uses an Internet archive as evidence of the web page's publication date. But if the web page actually lists a publication date, the Examiner might rely on that date instead of using an Internet archive. 

What if the date mentioned on the web page is not described as a "publication date," but as a "revision date"? As I mentioned in an earlier post (here) about the use of software screen shots as prior art, updates or revisions bring up another issue: it's possible that the piece of the publication relied on by the Examiner was not available until after the revision date because the revision date itself wasn't updated. In such a case, the Internet publication may not be prior art.

For software, Ex parte Martinez (discussed here) seems to say that the software copyright date is prima facie evidence, and the burden shifts to the Applicant to prove a later date. Ex parte Petculescu discusses the same update/revision issue for Internet printed publications rather than software, and shows that the same burden-shifting applies for electronic publications.

In Petculescu, the first page of the electronically published reference said "revised July 2001," and the Examiner used this as the publication date.

Appellants contend that Microsoft is not a proper § 102(b) reference because “[t]he dates of publication of allegedly relevant sections of the OLAP Article are not definable,” and because MPEP § 2128 does not allow a reliance on the revision date as the publication date (App. Br. 9-10.) The Examiner, however, contends that a publication date (“in the form of a revision date”) has been provided and Appellants provide no contradictory evidence. (Ans. 17.) We agree with the Examiner that Appellants have provided no evidence calling the revision date into question. Appellants merely speculate that this electronic document may have been altered without updating the revision date, they do not provide any evidence that Microsoft was in fact revised after the revision date (printed on Microsoft’s front page). Accordingly, we conclude that the revision date of July 19, 2001, is the date of publication of Microsoft.

Petculescu shows that you can't expect to remove the Internet publication as prior art unless you provide evidence that the portion of the publication relied on by the Examiner was actually added later.

Reexam/Reissue Blogs

I recently found two blogs related to reexamination and/or reissue topics.

Patents Post Grant is a new blog from the law firm Oblon, Spivak which covers reexamination and reissue. It offers lots of practice tips as well as coverage of BPAI, district court, and federal circuit cases involving reexam and reissue.

The Reexamination Center blog seems to post mostly about reexams that were recently granted by the PTO, and requests at district court to stay litigation pending reexam. But in addition to the blog, the website also includes a lot of information about the reexam process (FAQ, mistakes to avoid, etc.).

I've bookmarked both these sites for the next time I deal with a post-grant issue.

Examiner can't infer non-statutory embodiments (Ex parte Azuma)

Ex Parte Azuma
Decided September 14, 2009
(Appeal 2009-003902, Appl. No. 10/726,443, Tech. Center  2600)

I missed this decision when it came out, but I'm glad I became aware of it (through this post at 271 Patent Blog.) I can use it when pesky Examiners reject my computer-readable medium claims under §101 as allegedly covering a signal — when my spec never talks about a "signal" !

In Ex Parte Azuma, one of the claims recited "a computer usable medium having computer usable program code embodied therewith.” The specification referred to "such computer usable media as a distributed magnetic disk, an optical disk, semiconductor memory, or other recording media, or distributed over a network." The spec further stated that "the hardware configuration may include several storage media: main memory 103, hard disk 105, floppy/disk drive 109 and various other hardware configurations such as, a CD-ROM or DVD-ROM drive."

The Examiner rejected this claim under §101, reasoning that because the spec did not specifically limit the medium to a storage medium, the medium then includes a signal under the broadest reasonable interpretation. In particular, the Examiner pointed to the "various other hardware configurations" phrase in the spec. 

The Board acknowledged that computer instructions embodied in a signal are not statutory under In re Nuijten, but did not agree with the Examiner's interpretation of "computer usable medium." According to the Board, this term did not stretch to cover a signal in this instance because the "other configurations" were "hardware configurations," which implied a tangible embodiment. 

This case will be useful to those of us dealing with "software" claims, because it addresses the practice of an Examiner reading non-statutory signal embodiments into a claim. That said, don't assume all is well for computer-readable medium claims, since a number of BPAI decisions rejected such claims under §101. The most widely reported is probably Ex parte Cornea-Hasegan, which used Bilski to affirm a rejection of a computer readable medium claim, holding that "the analysis of a 'manufacture' claim and a 'process' claim is the same under §101."

By the way, if you want to know more about how the BPAI has been applying Bilski, check out this article reviewing BPAI decisions that discuss Bilski (up to Sept. 2009).

Does an RCE always buy two more rounds of prosecution?

Do you expect an RCE to buy you two more rounds of prosecution? That's surely what happens in the vast majority of cases. However, a strict reading of MPEP 706.07(b) seems to say that under limited circumstances, an RCE only buys you one round.

Takeaway: The Examiner is allowed to take you final on the first OA after the RCE if he doesn't find your arguments persuasive AND as long as one of two other conditions is met:  a) you didn't make any claim amendments with the RCE; or b) you made claim amendments, but didn't present them in an After-Final response.

Digging deeper:

706.07(b) Final Rejection, When Proper on First Action
The claims of an application for which a request for continued examination (RCE) has been filed may be finally rejected in the action immediately subsequent to the filing of the RCE (with a submission and fee under 37 CFR  1.114) where all the claims in the application after the entry of the submission under 37 CFR  1.114 (A) are drawn to the same invention claimed in the application prior to the entry of the submission under 37 CFR  1.114, and (B) would have been properly finally rejected on the grounds and art of record in the next Office action if they had been entered in the application prior to the filing of the RCE under 37 CFR  1.114.

Simply put, the first OA after an RCE can be final when a) the claims could have been finally rejected if entered prior to the RCE; and b) the claims are drawn to the same invention as before.

Before parsing these two conditions, note the same section of the MPEP lists an important exception:

However, it would not be proper to make final a first Office action in a continuing or substitute application or an RCE where that application contains material which was presented in the earlier application after final rejection or closing of prosecution but was denied entry because (A) new issues were raised that required further`consideration and/or search, or (B) the issue of new matter was raised.

The way I read this, you're safe from final-on-first-OA-after-RCE as long as you follow this procedure:

• File an After-Final response with claim amendments.
• Wait for the Advisory Action denying entry of the amendments.
• File an RCE to get those amendments entered.

Since this safe-harbor provision only applies when amendments or evidence was "denied entry," you're not safe if you argue without amending claims. In such a case, the Examiner can immediately take you final if he doesn't find your arguments persuasive.

I think there are reasons to prefer going straight to the RCE rather than taking the AF-AA-RCE route. One is that the AF must be filed within two months to avoid EOT fees. Even if you do hit the two-month date, you're going to owe at least the 1-month EOT unless you file the RCE on the very same day the PTO mails the AA.

So if you want to go straight to RCE, how can you reduce your vulnerability to final-on-first-OA-after-RCE? We need to parse the pair of conditions that allow final-on-first-OA-after-RCE:

• All claims are drawn to the same invention as before. 
• All claims could have been finally rejected if entered prior to the RCE.

I consider "drawn to the same invention" to be a term of art which refers to restriction practice. Thus, I'm hesitant to argue that some of my claims are not drawn to the same invention, even if doing so could avoid final-on-first-OA-after-RCE, because it leaves me vulnerable to a restriction requirement.

So let's assume that your claim amendments do meet the "same invention" prong. Even so, the Examiner can't take you final immediately after the RCE unless the second "could have been finally rejected" prong is also met.

Clearly, your claims "could have been finally rejected" if the Examiner finds all the elements in the references already of record. Put another way, if the Examiner has to introduce a new reference, he can't issue a final rejection, and you're safe.

Intuitively, you can see that the more your amendment changes claim scope, the less likely it is the Examiner can find everything in the references of record. In this respect, an amendment that adds a whole new feature is more likely to produce a new reference than one that merely clarifies something (e.g., "wherein the method is implemented in a computer" or "wherein the first and the second widgets are different"). Even when adding a new feature, you might want convince yourself that none of those secondary references discloses the added feature.

Perhaps a middle ground approach is the following. If you're making substantive amendments that narrow significantly, go straight to RCE because you're counting on the Examiner having to introduce a new reference. But if you're making smaller clarifying amendments, first try to get them in After-Final.

For what it's worth, it's rare that I see this final-on-first-OA-after-RCE situation.

What do SPEs do?

If you want to learn more about the role of SPEs (supervisory patent examiners) at the PTO, read the comment thread here at the recent Patently-O post about "rethinking the role of SPEs". 

It appears that a number of Examiners contributed to the comment thread. Sprinkled among the usual "what's wrong with the PTO" discussion between Examiners and practitioners are some interesting tidbits about the inner workings of the Examiner corps.

Follow-up on "each" in a claim

Previously I discussed In re Skvorecz (here), where the Federal Circuit interpreted "each wire leg having X" to mean "every wire leg having X". I found this outcome surprising, as did many of my colleagues. So I decided to dig deeper into this topic.

Takeaway: Though not cited in In re Skvorecz, the leading case on the meaning of EACH is ResQNet.com, Inc. v. Lansa, Inc., 346 F.3d 1374 (Fed. Cir. 2003). According to ResqNet, EACH OF A PLURALITY OF Xes means SOME OF THE Xes, where EACH X means ALL Xes. To be safe, reinforce these meanings by using words like "some," "all," and "every" when describing the feature in the spec.

Digging Deeper: Why was I surprised at the Skvorecz conclusion that "each" means "every"? In a word: "comprising." That is, doesn't black letter patent law say that when "comprising" is used, additional elements are irrelevant? In the Skvorecz case, isn't it irrelevant whether or not additional legs have X, as long as the claimed "plurality of legs" have X?


Actually, it's more nuanced than that. A device including unclaimed elements still infringes when "comprising" is used as the transition. Crystal Semiconductor Corp. v. TriTech Microelectronics Int'l, Inc., 246 F.3d 1336, 1347 (Fed.Cir. 2001). A device including additional instances of a claimed element does not escape infringement when the article "a" is used, absent a clear intent to limit the article. See KCJ Corp. v. Kinetic Concepts, Inc., 223 F.3d 1351, 1356 (Fed. Cir. 2000).

ResQNet, Inc. v. Lansa, Inc. addresses additional instances of a claimed element introduced by the article "each." ResQNet interpreted two similar claims that used "each," with opposite results.

The ResQNet Court found EACH = EVERY in this claim:

means for receiving information to be displayed as a first image on a screen;
means for processing said information to generate a screen identification (“ID”) from said first image, said ID being generated as a function of the number, location, and length of each field in said first image ...

The Court said the claim language itself dictated EACH = EVERY: "This [claim] language shows that the claimed algorithm evaluates attributes of each (and every) field in the information to be displayed, i.e., the first image."

Yet the ResQNet Court found EACH <> EVERY in this other claim:

means for identifying, based upon a position, length and type of each of a plurality of fields, a particular screen to be displayed to said user;

See the difference? It's EACH OF A PLURALITY OF FIELDS versus EACH FIELD. The Court focused exclusively on "plurality":

Claim 1 of the ’608 patent recites “each of a plurality of fields,” which does not carry the same meaning as “every field.”  Rather, the recitation of “plurality” suggests the use of “at least two.” ...  While “at least two” may mean “every” under some circumstances, the two terms are not synonymous.  In sum, “each of a plurality of fields” means “each of at least two fields.”

At first I didn't see the difference between the two claims, because I was *inferring* a plurality when I read "each field in said first image." But in fact, this claim never says plurality of fields, and is in fact agnostic as to how many fields there are. Once I realized that, the Court's construction made more sense.

Note that the Court bolstered its interpretations by referring to the specification. For the EACH = EVERY claim, the Court found that:

The specification confirms the “all fields” requirement in the ’961 claim: "In describing the determination of the screen ID, the specification provides that “the particular screen [is identified] by its layout, fields, etc." and " ... From the display buffer, the program derives the following information: ... b) type of each field ... With the words “each field” and “fields,” this passage suggests that characteristics of all, not just some, fields are inputs into the algorithm. Nowhere does the specification suggest otherwise.

Do these passages really confirm that EACH = EVERY? To me, these passages shed no light at all, one way or another.

Contrast this with the spec for the EACH <> EVERY claim. The Court found that:

The ‘608 specification confirms this meaning of the claim language. In the only portion specifically addressing whether the algorithm employs all or some fields, the specification notes that “the personal computer analyzes the screen with respect to the location of particular fields.” This passage suggests that the PC selects certain fields – potentially a subset of all fields – for analysis.

I do agree that "particular fields" suggests not every field, so that the '608 spec supports EACH <> EVERY.

Would a different result be reached with a different description in the spec? Because I don't buy the Court's single-minded focus on the word PLURALITY in the phrase "each of a plurality of fields." After all, the word EACH is present too, and the Court didn't satisfactorily explain to me why PLURALITY negates EACH.

Adding claims to different invention during prosecution

If you've been practicing for more than a short time, you're familiar with restriction practice: the Examiner takes the position that your claims are directed to more than one invention; the Examiner issues a restriction requirement; and you're forced to elect a subset of the claims to continue prosecution.

You may not be familiar with the less-common "election by original presentation," in which the Examiner elects the claims. Now, it's not as bad as it sounds – this can happen only in limited situations, and the Examiner can't just elect any subset he wants.

Here's the deal: the Examiner is allowed to use election by original presentation (described in MPEP § 821.03) when you add claims that are directed to a different invention than the one you originally started with. The idea is that the Examiner already searched the original invention, so you can't pursue the new invention in this application, even if you want to. So the Examiner elects the claims directed to the original invention and withdraws the other claims.  The MPEP instructs the examiner to use this form paragraph:  

Newly submitted claim [1] directed to an invention that is independent or distinct from the invention originally claimed for the following reasons: [2]
Since applicant has received an action on the merits for the originally presented invention, this invention has been constructively elected by original presentation for prosecution on the merits. Accordingly, claim [3] withdrawn from consideration as being directed to a non-elected invention.

If you disagree with the Examiner that the new claims are directed to a different invention, you have the same recourse as for the standard restriction requirement: you request reconsideration and provide arguments why the restriction is improer, and then you petition if that fails.

What is a "newly submitted claim?" Is it limited to new claims added during prosecution, or does it cover an amended original claim? I don't know the answer to this, but it makes sense to me that the Examiner could also use election-by-presentation when you make amendments to an existing claim. After all, we've all seen amendments that replace 90% of the words in the existing claim, right? How is that any different, substantively, than a new claim?

Not being allowed to pursue newly claimed subject matter as a result of election-by-prosecution by the Examiner is annoying enough – but there may be worse side effects. To begin with, you can get slapped with a non-responsive amendment if your response cancels the claims directed to the original invention and thus includes only claims directed a different invention. Here's the Examiner form paragraph, from MPEP § 821.03:

The amendment filed on [1] canceling all claims drawn to the elected invention and presenting only claims drawn to a non-elected invention is non-responsive. The remaining claims are not readable on the elected invention because [2].
Since the above-mentioned amendment appears to be a bona fide attempt to reply, applicant is given a TIME PERIOD of ONE (1) MONTH or THIRTY (30) DAYS, whichever is longer, from the mailing date of this notice within which to supply the omission or correction in order to avoid abandonment. EXTENSIONS OF THIS TIME PERIOD UNDER 37 CFR 1.136(a) ARE AVAILABLE.

Worse yet, if you file an RCE in order to get those new/amended claims entered (the ones directed a different invention), and then the Examiner withdraws them from examination...you've wasted an RCE fee. You'll need to file those claims in another application, and you don't get your RCE fee back.

If the Examiner balks at your claims directed to a different invention, make sure that the Examiner actually issues an Office Action with a restriction-plus-election-by-presentation. What you don't want is a generic Office Communication simply informing you the response is non-responsive because the only claims in the case are directed to a different invention. (See the file wrapper for 11/300,970 on PAIR for an example of this.)

What's the difference? An important one: only an actual restriction requirement allows you to file the restricted-out claims in a divisional rather than a continuation, which in turn avoids protects you from a double patenting rejection.

I don't know how common Examiner election-by-presentation practice is. It's happened to me only a handful of times. But it is something to think about when adding lots of new features to your claims.