Well, after some of the clues pirate posted, having big influence at Mt.Gox or some other large exchange, he might be doing
Front running which is extremely profitable. The only risk is when the bitcoin price goes up steeply, he runs out of bitcoins and BTC price continues to climb, so he's unable to make profit in BTC and pay his lenders. Front running is common practice at bitcoin exchanges, with large order you will never get market price, they will take their share of profit
He may even operate on many different smaller exchanges and take advantage of the information he has to increase his profits and lower the risks. So, does this theory fit? Pirate, the big market manipulator. The more bitcoins we give him, the more power he has to screw the market participants.