In some ways, restriction requirements can cause more delay and increase costs more than prior art rejections. At least with prior art rejections you have the option to appeal to a purportedly unbiased decision maker (PTAB) judge, who is hopefully kept in check via its overseeing court, the Federal Circuit. Such appeals do occur on a regular basis and the Federal Circuit, at least in some cases, keeps the USPTO in check (e.g., in rejecting overly broad interpretations as unreasonable at least in some cases). This is not true with respect to restrictions. As discussed in previous posts, restrictions can only be petitioned to another government bureaucrat in the Office of Petitions, with no pause in the applicable deadlines. This alone makes such a path for review effectively unavailable in many instances.

Nevertheless, Petitions for review of restriction do have a place and even the Office of Petitions has shown that it will sometimes provide a meaningful check on unreasonable examiner behavior. One area of seemingly inconsistent review, however, is with respect to the search burden requirement. As discussed in a previous post (here), and as set forth in MPEP 803, every restriction requires not only distinctiveness, but also that there be a serious search burden.

One would think that if an Examiner required a restriction, and then after traversal failed to allege any specifics to support a search burden, that the restriction would be improper. In practice it is possible for applicants to file and win petitions in such circumstances. A recent example is from Apple in SN 14/475,445, which claims methods for presenting alerts. Apple presented a nice petition that pointed out (in their petition, here) the complete lack of analysis on the part of the Examiner with respect to the search burden (the petition also provided good arguments against the Examiner's reasoning for the restriction in the first place).

The Office of Petitions agreed and confirmed the restriction should be withdrawn because, among other reasons, the Examiner did not provide sufficient reasons or examples to support the search burden.  

However, one must be careful because the Office of Petitions will often tolerate even the most minimalist explanations from Examiners. Sometimes the Office will even provide more detailed (and new, corrected) reasoning in a decision dismissing the petition. Further, the Office of Petitions will even deny petitions where it is accepted that the search will not be burdensome if the application of the search results will be burdensome. See the following reasoning in the denial of a petition in SN 14/460,576:

Where the Office derives authority to expand the search burden to the effort in applying the search results is not provided.

So, consider strategically utilizing petitions as part of an overall prosecution strategy, as is clearly done by Apple.