I am new to all of this so please forgive this question if it seems naive. I have looked at three exchanges (MTGox, BTC-E, and a third one).

I am looking at the prices of the bid and ask at each of the various exchanges. Currently there is approximately an $8 spread between the highest exchange price and the lowest exchange price for Bitcoin. Can somebody simply buy from one exchange and turn around and sell on the other exchange and pocket the spread? Or am I missing something?

Thanks