Another example: currently there is about 30% arbitrage opportunity between BTCChina and bitstamp. That is, there has been more than $100 difference in the pric

Another example: currently there is about 30% arbitrage opportunity between BTCChina and bitstamp. That is, there has been more than $100 difference in the price of Bitcoin between those markets. If you know how to move money quickly between those locations, you can make lots of money. It isn't easy problem, because otherwise the arbitrage opportunity wouldn't exist.