I'm not quite so cynical as to think these petitions couldn't possibly matter -- though I admit, evidence that they do is rather hard to come by -- but I think that if the Administration responds to one at all, they'll ask themselves "what is this petition actually trying to accomplish, and what can we do to further its goal?" I.e. even if they do feel prompted to do something, they won't feel bound at all by the specific policy proposal. This is Government 101; I don't think we need to worry about it.
The point of the petition, then, is simply to establish how many people care about the issue in the first place, at least enough to click on a web page.
Right; and in this case, I believe that "man, people really care about cell phone unlocking, maybe we should as well!" is more likely to cause the legislation similar the Canadian act ("carriers must unlock if asked", "carriers must be very clear about unlocks", etc.) than anything related tithe DMCA ;P. That's the problem with such a narrow focus: there are more direct solutions to this particular problem that are more likely than DMCA changes that seem to pacify the petition.
(You may have just been demonstrating the efficacy of a petition in the abstract, though, and not about this one in particular. I will then just say "noted", and point out that if this had been "dismantle the DMCA" or something, I would have lent my support to it, despite it being a White House petition ;P.)
The point of the petition, then, is simply to establish how many people care about the issue in the first place, at least enough to click on a web page.
(Helpful analysis, though; thanks.)