Yukon, situations vary of course but often what you are seeing are MMs showing 100 shares because they have no current active desire to trade a stock, but are required by regulation to make a market. 100 shares is often the minimum that can be displayed to retain the market making right.
>Suppose that two market makers have asks
>of 100 shares each at 2.35 and 2.36. I have
>an ask on the Island at 2.37 for 1000 shares.
>Then some guy comes along and places a
>market order for 1000 shares. What happens?
(for the moment, let's not confuse your described "market order" with some direct access broker provided market order mechanism which may break your order down into a whole bunch of ways, but rather let's stipulate that the market order reaches a MM whole.)
(also, lets say that after your 2.37 X 1000 share ask, the next ask is 2.44 X 100 shares followed by 2.45 X100, 2.47 X100, 2.48 X100 and ECN - 2.50 X 600)
That will depend on which MM get's the "market order". MM may fill order from inventory at something near the inside. MM may know of another MM that is looking to do more than 100 share business and fill that way. MM may take out the two MMs, hit the Island ECN order and take it out (eating the 200 shares for the moment). Now of course, the inside ask is 2.44 and he can fill the 1000 market order out of inventory at about 2.48 (the average of the next 1000 shares) and make a Benji on the deal.
There are a thousand other posibilities as well.
JB