They are phantom asks, not bids, currently. And if people are using the mt gox interface they keep trying to buy at the price 16.75, when no one is selling that low.
Ah gotcha, sorry I didn't read your title well enough. I wonder if people are doing the reverse of the exploit. Putting up an asking price, withdrawing all their BTC's and hoping the order fills and they get cash with no BTC's in the account to debit? Although if that's the case, why use such a low number of BTC's? I would think they would try to get as close to that $1,000 limit as possible.