It is easier to manipulate a stock when its volume is low. All a manipulator needs to do is execute a few carefully timed trades to create the illusion that a stock is moving so he can get others to buy or sell. The goal is to raise the price if he wants to sell and to lower the price if he wants to buy. If you are suckered in by such a move, your position can quickly turn into a loss as the stock you just bought suddenly reverses course on increased volume.