I've never understood how people
can visit an illegal gambling site and not expect to get taken. (Granted, even visiting a legal gambling site is an invitation to be taken, but at least it usually has some parameters established for the maximum they can take from you.)
Now, before you go off on a BitCoin is legal rant, please note that is quite beside the point here. Mt. Gox were known to be engaged in shady dealings. Such dealings are normally in an accepted currency. So it's not so much the currency as those other dealings which are the problem.