Not the heist itself, but the consequences of that heist. So basically a bunch of theives with guns and a scary mask sneak into the stock exchange to ruin Bruce financially but using his finger prints to execute risky bets that wouldn't pay off so they could ruin him financially. Fair enough.
HOWEVER, I'm not a market expert, but I'd be willing to go out on a limb and say that every trade executed that day would be voided. I like how Morgan Freeman says we "might" be able to prove fraud. Might. MIIIIIIGHT?! They have those dudes on CAMERA, there is no might. Any *beep* agency would know it was absolute FRAUD!
Fox: "If you look here on the video, after the smoke clears... There! There, the man in the leather jockstrap mask? He is clearly NOT an authorized trader..."
Investigator: "Eh... I dunno... maybe..."
Sure it was fun to watch, but completely unrealistic for a film that strives to be intelligent and as real as it can be in terms of comic book films. I feel like Nolan only made it in order to make a slight commentary on occupy wall street when they cop says "But I keep my money in the mattres" and the other dude replies, "It doesn't matter, it will be worth nothing!"