I have found this to be the case in practice as well.  The smaller exchanges usually follow the larger ones.  The problem is usually the market dept is shallower so you may not be able to fill your whole order at the price you want.  It also depends highly on which way the price is going though because it's really easy and fast to move BTC between exchanges, but cash moves slow.  Even though I sold my BTC for a higher value I can't move my cash to MtGox to take advantage of the lower price.  Also if the large exchange bottoms out quickly and the rises the small exchange will bottom out at a higher value.