Bid/Ask fluctuating, but very little volume is crossing the tap. MM's can move bid/ask without a single trade taking place. Sometimes they do this in order to give the appearance that the stock is moving higher or lower. For example, they can move the ask from 42.35 to 42.40 without a trade crossing the tape. They would do this in order to make it seem as if the stock were going up - hopefully to try and get the public to buy at the market so they can sell at a higer price.