The Bid-Ask spread is the difference between Bid and Ask, and the wider the spread, the less liquid the stock is. A wider bid-ask spread indicates more volatile and less liquid security. Traders may not execute trades as often when there's a large spread, and when they do, the price may jump around more quickly than a more stable stock that only moves a few pennies at a time. It's hard to predict what price you'll get with a market order, and stop orders are less likely to arrive precisely at the stop price you specify.