Arbitrage trading should be profitable due to the difference in price between the exchanges. The basic principle is to buy BTC at one Exchange for a certain price (1200) and transfer to another exchange where BTC is worth more (1250). Once your bitcoin are at the 2nd exchange one transfers to USD and you should be able make the difference. Two problems. One needs high volume to make a good profit and one needs to be quick from 1st step to last. It is not as easy as it sounds.