Market orders in Cryptsy and BTC-E Looking at the dynamics of the Cryptsy and BTC-E trading engines you aren't able to place market orders.  The orders just seem to be limit orders at the best market rate.  For example, I want to buy 20 bitcoins at $700 and the best offer is $700 with 15 coin volume.  The offer should get knocked out and the remainder of 5 should be subtracted from the next best offer.  

My question is why this doesn't seem to be the case with BTC-E and Cryptsy?  If your order volume at market is greater than available volume at set rate it sets up a limit order until the order is filled.  

Can anyone confirm this and explain why they do it?
There's nothing a market order can do that a limit order can't do. To place a market order, just place a limit order for the amount you want to buy at the worst price you are willing to pay.