So it turns out that in the upcoming PS3 sequel, inFAMOUS 2, your morality will be determined by how you react to either the devil or the angel on your shoulders. Well, not literally, but you have two NPC characters who will offer you choices. Kuo is an NSA agent working to help you defeat the Beast. Nix is your hedonistic guide that coaxes you into not thinking about the consequences of your actions. So at various points in the game, you'll choose whether to follow the path of good or evil. And don't worry, apparently you can always change your mind and veer back onto the side of good (or evil) depending on your mood.
It's a shame that it seems to be so hard for developers to make morality choices in the game a little more transparent. The Fable series is the worst. Their moral conundrums are so obvious it's embarrassing. I feel like BioWare is the best at it, like in Mass Effect 2, when you have to decide whether or not to commit genocide. And your choices will come back to haunt you, too. I also found myself taking extra time to weigh some of my decisions when I played Heavy Rain. I much prefer that kind of storytelling to the very clear-cut good or evil choices. And especially here in inFAMOUS 2 where they make a point of reminding you that your actions won't have consequences because you can always switch onto the other path whenever the mood strikes. What's the point of that?
inFAMOUS 2: Morality Revealed, Meet the Companions [PlayStation Blog]