If you're on the PS3, your chances are practically one in a billion.
From what I read (I keep updated on the PS3 forums) no-one has been banned for prestige hacking.
So many people do it now that it's impossible to stop really. The thing is that Sony can't tell who hacked, they can only stop them from doing the hack by releasing patches. Even then we can bypass the patches.
In simple, there's practically no chance you will get banned. Look at Hunter128 and theUnknown who openly admit to having challenge lobbies. You would think Sony would track their IP and ban them right? Wrong.
My point
/AC