Wow, I wasn't aware that you can withdraw 40kBTC and 40kUSD while having an anonymous account at MtGox. The same MtGox that is known for their extensively KYC and AML... Maybe you know something that we dont?
It wasn't an anonymous account which withdrew the money. It was the Bitcoinica account which had trusted status - at one point the limits for trusted status were $100,000 and BTC 40,000 daily. They've been revised since then and yet again after the hack. you need to remember that as far as MtGox's computer was concerned it was Bitoinica making the withdrawals and Bitcoinica had a history of moving large amounts on and off MtGox. It's possible that there even more funds in the Bitcoinica account but the hacker was unable to access them because of the daily limits.