Oh I agree with you. But that's what makes the whole petition thing a great PR machine. I'd argue that almost any change people are requesting will require at least some level of approval from the legislature so Obama can say "Oh, I agree and am as passionate about (insert topic here) as you are, but that do-nothing congress, well, sorry but we can't do much..."
It's not that it's Obama's fault but I find the whole thing disingenuous at best, similar to his campaign messages* that got everyone excited enough to vote for him.
* And here again there are really no differences between either party, or one politician over another.