Not that I have trust issues or I doubt the sincerity of exchanges but it's not too much to think otherwise that is it possible that these exchanges are staging the siege?
An exchange is like a bank. Unless you build iron strong security, backups and all sorts of mitigations should a break occurs, you will go down. Mt.Gox went down in history for such thing, and there is been more and more of the same.
Do you trust your exchange? You shouldn't.
Actually the same applies to any online wallet.
Do you think some dubious person staged an attack to his own service? I wouldn't be surprised of that either. "I got hacked" declare bankruptcy, and years later the guy is living a rich life somewhere...