There's also no reason to keep BTC or USD at any exchange for more than the time it takes to make a trade, unless you're arbing between exchanges (in which case

There's also no reason to keep BTC or USD at any exchange for more than the time it takes to make a trade, unless you're arbing between exchanges (in which case this type of event does suck but should have been priced into your whole strategy). Mt gox was an exchange not a bank.