But it seems like if they were pumping the price up, then a lot of active traders would be holding fake USD. Mt. Gox can't tell if it is accepting real or fake USD while dumping. I think my first post outling a possible scenario that generate nothing except perceived loss to users once they can't withdraw.
When a user does not yet have sufficient USD on deposit with Gox to buy the bitcoins they want, they deposit more, and MtGox now has more real USD under their control. It's not a matter of selling the coins for real vs fake USD.
