Wasn't there a huge incident when an auditor's account got hacked and lots of BTC was stolen? Was that Mtgox? Sorry don't recall the exchange without looking it up.
I think this is what you're referring to:
http://www.youtube.com/watch?v=T1X6qQt9ONgThey used the account to clear the whole orderbook.
/Edit: I still think Gox tried to cover up the real reason for this. It just makes no sense to give auditors 500k bitcoin and allow them to trade them on the live system. Whatever...