My conspiracy theories side tells me this: imagine that you own a bank that is not guarded by any rules laws or regulations, that most money is deposited anonymously or semi-anonymously, and it is deposited in unmarked banknotes. And its worth $500k.
Now, fast forward to today and you keep keys to $400,000,000 vault. Only rules haven't changed. Now, given the overall complexity of bitcoins algorithm, the fact that mt gox is (afaik) not even registered in a country with solid laws, wouldn't you grab the money and "run", even though running means only pointing out there was a glitch in the system and filing for bankruptcy protection?
If any of this is true, then here is your (sad) reasoning why we need government oversight when it comes to dealing with someones property, being it even bits on someones hard drive.