but there are not enough real BTCs on their own exchanges. doesn't matter how low the price drops, if they don't have enough BTCs to cover the total clients BTC deposits, they will have to buy externally. nobody is depositing BTCs into gox to sell at 250. the only way they get more BTCs is to buy externally.
What do you mean by "there are not enough real BTC on their own exchange"? Worst case, they have to come up with BTC equal to the sum of all BTC balances of their customers accounts. They can reduce these BTC balances by using their fiat on their exchange to buy BTC.
exactly, and how low must goxBTC drop for gox to cover their short? can this be done before the exchange gets shut down? if yes, then buy goxBTC! if no then sell! game of chicken.. kinda like merger arbitrage, post announcement.