LOL exactly what I've been thinking hahah. Unless of course it is MtGox themselves doing it and they just give themselves the money. It would seem to either be MtGox doing this to help themselves in some way, or someone or some organization that wants Gox or BTC dead. Though if it was an organization that wanted BTC dead, you'd think they'd just put these sell bots on every exchange and not just MtGox .
Are you SURE it is really a bot, and a single one at that? And are you sure it is doing no buying? They can't sell too much for too long, noone has unlimited funds.