At the time of writing the price on MtGox is $2.40 - on Tradehill its $2.18 .
Since you can move money to tradehill instantly using BitInstant (which I just did and bought at $2.17), why isn't everyone doing this?
Really my question is, why is there often such a gaping price difference between exchanges when the whole point of bitcoin is that you can move them around so easily?
For the last week or so the price on Intersango was at least 10% more than on Mt.Gox - it's trivial to buy coins on mt.gox, and sell them on Intersango in GBP - wait for price parity, buy them and move them back to USD on Mt.gox.
Why aren't people taking advantage of the mobility of Bitcoins?
