Au contraire, my FRiend.
"Mt. Gox, once the world's biggest bitcoin exchange, filed for bankruptcy protection in Japan on Friday, saying it may have lost nearly half a billion dollars worth of the virtual coins due to hacking into its faulty computer system."
That’s because people were using Mt Gox like a bank for convenience and allowing them to hold on to the keys. It defeats the entire purpose of cryptocurrency.
If your key is not stored online, nobody can hack it.