Part of the "mystery" about MM's is the alleged tactics they use to keep up volume in a stock.
for example say they have a load of buy orders for Tecz sitting there at .90 and some sells up around 1.25 but last price is at 1.11. Do they not try to entice buyers and sellers to meet by moving up/down the bids and the asks? Try moving up the bid and the ask until some buyers "think" its going up so they increase their bids. "Shake" out some sellers "walking" the PPS down to where the buyers are or to take out the stop loss orders. All in the name of making a market and increasing volume as they get a small cut of all trades?