An excellent explanation of how MMs exploit volatility. They are essentially buying shares on credit due to demand when they lower the prices, and then selling for cash to the investors that think it is a good price. When they lower the stock a few more points, some of the investors sell back to the MMs. This gives them a lower average on all the stock they own. Eventually their average reaches a low enough point that they can sell over time on a spike above the average buy in price. Pocket the difference and find another stock...boom boom.
This really does explain why bottoms seem to drop out when a stock is being talked about on message boards. They see this as an opportunity to lower their average due to the increased investor interest in the stocks. (i.e. LGTT)