Quote from Scalper007:
It's always been like that in nyse stocks. When the stock is moving up fast, the crook freezes and then spreads up and fills you at the nastiest price possible. So use the ecns during violent moves. Actually the hybrid is supposed to make this "ask freezing" thing disappear. Because now your orders will get filled in a second like in nasdaq. The specialist ask just jumps to the next best ask on the book. And the specialist(or specialist bot) rarely ever freezes. If you traded MA the past couple of days, you'll know what I mean. Its a hybrid and when you place a market order, he fills you at the best prices on the book. So if he is showing 100 shares at 74.50, and you place order at market for 500, you get 100 at 74.50(if you're lucky) and if next ask is at 74.60, you get that and if that 74.60 was cancelled by the seller, then you get the next best ask maybe at 74.75. He rarely stops to add lquidity or give any price improvement. You just get what's there, so you have to be much much more careful with market orders. When change comes, good and bad will come with it. The good being instant fills and the bad being uncertain prices. We just have to adapt...I don't even know if I can adapt to this speed, its just incredible. Or maybe MA is just a low float maniac coupled with hybrid which makes it crazy..