What would motivate someone to steal Paypal accounts and then buy lots of Bitcoins at MtGox? What's in it for him? He knows that because of the 30 day freeze he will never see any coins. All he can do is shake up the market and cause grief for the MtGox owner.

That would be a hell of a determined troll who is prepared to commit a criminal offense just for a little bit of lulz.

you never heard of 4chan, did you ?