This is not exactly true. I believe MTGox uses offline wallets for the storage of the funds, and I'd expect any other sane bank use it as well.
If someone breaks into the MTGox, they'll be only able to steal the "reserve". To get to the real money, the MTGox admin has to physically go into a vault (safe), and retreive its contents.
If someone breaks into the MTGox, they'll be only able to steal the "reserve". To get to the real money, the MTGox admin has to physically go into a vault (safe), and retreive its contents.