He turned on his TV. The price for Facebook was hovering at $39 a share. He placed a market order online for 128 shares. Then he realized he had made a mistake. He should have placed a limit order. A market order could fill at ANY price. A limit order could fill at a price no higher than HIS limit price. The order hadn't filled yet. He tried to cancel his order. It didn't cancel. He called his stockbroker. He explained his problem to the representative. She said, "Don't worry. All market orders are time-stamped. For example, let's say the shares were $39.10 at 11:30. If you placed a market order at 11:30, you would pay $39.10. Not a penny more." He said, "Are you sure? I've never heard that before." She said, "Count on it." He felt better. Later that day, his market order filled at $44 a share.