I can understand MtGox shutting down there exchange after it appears to have been compromised but then another exchange (Trade Hill) shuts down temporarily?
I cant help thinking they freaked that if the exchange was allowed to stay open people would actually have finally realised that Bitcoin is not actually worth anything and dumped the rest of there holding at knock down prices. When prices fall so to will the exchanges commission – its in a Bitcoin exchanges interest to keep exchange rates high.