FYI, on The Bitcoin Show tonight, one of the Mt. Gox guys said that the ~400k transfer was them taking security measures by moving their BTC to a different wallet.
Someone else said it was a certain "Adam" on the show who said the 432k BTC txfer was MtGox transferring as a security precaution. "Adam" is not related to MtGox.
(Sorry I forget where I heard about this Adam. I'll try to get clarification about this transfer.)
But regardless, it worries that it was made (a minute) before MagicalTux appeard on IRC, where he was clearly just discovering the selloff, and hadn't started his investigation yet. Also it doesn't make sense that a "single account" was compromised and had hundreds of thousands of BTC in it. No one in his right mind keeps this amount of coins on MtGox (other than MagicalTux himself?), ask knightmb how he secures his 370k BTC
