That's thinking really far, good stuff. The trading company (Ameritrade for example) insures up to a certain point. Ameritrade wouldn't let you make that trade if you don't have enough capital to back that trade. Lets say you somehow managed to do that trade, and you declare bankruptcy. I think then Ameritrade would have to cover that cost. Then if they can't, then Ameritrade declares bankruptcy. That's as far as I reasoned.