commissions are wayyyy lower...it often takes minutes only to break even
+1 on this. Commissions on all BTC exchanges are shameless, up to 4-5x higher than on forex exchanges. They are getting lower as competition of quality exchanges mounts up after Mt. Gox disaster, but probably has to be lowered more to some sensible levels. Right now you have to catch almost 10 US$ price difference just to break even (profits go to commision) on one buy/sell cycle.