This is not illegal. However, if this were an NYSE listed stock, the specialist would catch on eventually and just start filling their orders with his own inventory. The specialist can see everyones ID when they send an order and they tend to memorize the size player's IDs. Thats the beauty of having a buyer and seller of last resort, he can cut down on the bullying of the stock. If it's a NASDAQ stock, then you are screwed. This kind of bullying can go on for awhile unchecked because other market makers enjoy the increased volitility and will probably not gang up against the bully. That's why NASDAQ stocks appear to have more manipulation than NYSE stocks.
