Quote from Don Bright:
OK guys, here's a look at "Bright Trading 101" - when we want quick executions on the NYSe, we submit bids higher than the offer ....why you ask?...simple, because the assistant specialist can simply click a "fill" at the best current price, giving us almost immediate gratification...and, if were to use market orders, the Specialist himself (herself) has to determine the price, which may take a while for him/her to batch the orders.
So, very simply, we want quicker executions, often with price improvement. You will see those order for a few seconds on the L2 or NYOB at times. Works on ECN's too.
Don