While I understand (and often share) your cynicism, change.org has won some victories in the past: http://www.change.org/victories
The level of the "victories" do vary. But, in this particular case, I think a mass expression of support for this girl could actually encourage the local DA and school reconsider moving forward with prosecution.
Perhaps steer clear of questioning whether he was correct to guess your meaning when following it with a line that confirms you were indeed being cynical. Not saying you are wrong to be cynical, but you are (as am I).
As I understand it, a big part of change.org's model is building a political mailing list, so they can follow up with you at election time and say, "you signed this petition that we sent to this politician, and they [did/didn't] do what you wanted." So even if the petition itself doesn't do anything, they can follow up with pressure at the ballot box.
A ton of mainstream product advertisements got pulled from conservative radio after Rush Limbaugh did that whole Sandra Fluke thing. That was spearheaded by change.org.
Agreed, I honestly don't think there has ever been any actual "change" occurring due to these petitions. They either are on the side of agreement with those in office, or they are not. The response is always a regurgitation of their current views on the matter.
Honestly, the best way to make a difference with local government is either to make a credible threat of suit or just make their lives miserable for a few weeks (by publishing their email addresses and phone numbers and sicking the internet on them).
I had a few altercations with my high school administrators. The first involved a student petition, the second involved formal letters from attorneys. Guess which one had more effect.
Edit: nevertheless, I have signed the petition in question.
Slactivists feeling good about themselves, primarily.
I say this not to tease about the goals and causes, but just that sending individual, targeted letters to the parties involved or a dollar to the family for their legal fund would do so much more. Internet petitions do nothing and are easily ignored.
I imagine that the abstraction of the reason is probably similar to the Fight Club quote about automotive recalls:
" A new car built by my company leaves somewhere traveling at 60 mph. The rear differential locks up. The car crashes and burns with everyone trapped inside. Now, should we initiate a recall? Take the number of vehicles in the field, A, multiply by the probable rate of failure, B, multiply by the average out-of-court settlement, C. A times B times C equals X. If X is less than the cost of a recall, we don't do one."
It's a similar thing with politics.
Just change A out for either people in the voting body or lobbying body, multiply by B, the probable percentage of A that you'll lose with a specific decision, then multiply by C, the amount of money (weight of a specific vote) that the specific entity would lose you.
If X is enough money/votes to win the next election, then business as usual. Of course one could say that Obama is done after this term anyway, but I have a feeling that the PTB have their best interests in favor.
edit: You've gone and deleted your post. The general gist of the question was: "What are the political forces in play causing him to change his mind about GITMO?"
