You can't do arbitrage if you can't get your dollars out. If you buy Bitcoins for $100 and sell them on Mt. Gox for $120, you're making money on paper but you c

You can't do arbitrage if you can't get your dollars out. If you buy Bitcoins for $100 and sell them on Mt. Gox for $120, you're making money on paper but you can't necessarily get your earnings out into your bank account. You'd quickly run out of capital, and in the end you might have your dollars seized.