Let's be honest, Activision has apparently done a slapshod job on one of the versions of the game. Not going by the petition itself, but by some of the sources quoted. It's not surprising that they would cut corners on one of the "lesser" platforms and exploit consumers, because that kind of greed is in keeping with the kind of thing Activision does right now. These are the guys who want to charge people for cut scenes, and who raided Infinity Ward with thugs because they didn't want to pay promised bonuses. Neither of these accusations are false either, The Escapist covered both of them.
This is also the company that had people going "WTF, $15 for a couple of maps" at one point. Another map pack was called the "Stimulus Pack" which had certain people talking about how they didn't even bother to hide what they were doing.
Yet people keep buying from Activision, and wih Activision getting away with it you have companies like Capcom going "hmm, well let's keep some of the most popular characters we're making out of the game and sell the singly". I wouldn't be surprised if during their board meetings they are looking at what other companies are doing, and referance "Hey, look at Bobby Kotick, he's a huge jerk with stuff like this and making millions for Activision. Gamers are stupid cashbags!".
Understand, right now it's the PS-3 users getting shafted apparently. However given Activision's track record, next time it could be you. Sitting there and saying "oh quit the whining" is exactly the kind of response you WOULDN'T want to get if you were the ones feeling wronged. Sadly it's a lack of any kind of solidarity even on important issues or when we're being exploited that allows this kind of thing to happen.
It's probably hoping for a bit much, but a petition is liable to go nowhere. Simply put, next time Activision releases a BIG game or sequel, don't buy it. Don't buy the next "Call Of Duty" game, no matter how awesome this one is, or how awesome that one promises to be. Your not doing it because of the games, but the company. A year or two of patience and supporting less exploitive companies can work wonders. Imagine a "Call Of Duty" with what would be all those extra maps included in the game to begin with....