My mistake then. But again, the risks are almost the same. MtGox fiat account could be seized, the entire site hacked and become insolvent, or his personal account hacked. If he intended to keep a fiat balance, it would be safer to do so in a traditional bank that can reverse transactions.
Perhaps he was keeping his fiat there because of MtGox's liquidity problems. Or perhaps he was a day-trader. These possibilities make it much more understandable.
But if you have fiat on Gox and you're not willing to spend this money any time soon, then I'd advice to withdraw it. Even if takes months to come to your bank account, it's safer like this than letting it sitting there. I'd say that MtGox is more vulnerable to account seizures than most banks... it has already happened to their US-domiciled accounts, are you so sure it won't happen to their main accounts in Japan?
There are millions of dollars in fiat sitting in MtGox accounts with bids placed on various price points from just below the current price right down to just a few cents per Bitcoin.
This is how any exchange works. It can't work without large amounts of fiat being on the exchange at any point in time otherwise there would be zero liquidity and no bids.
This issue needs to be addressed properly due to the millions of dollars in fiat which is properly stored on the exchange and must remain there for normal liquidity and trading to continue.
If everyone withdrew all their fiat the price would be back in cents per Bitcoin before you know it. It's just not feasible.