Once through a broker, mind you, i put a sell order of 1,000 shares from my total of 10000 from a particular co. When I received the sell contract I saw he sold all my shares. He said i said 10000 and i did not. That same day those shares went up 6c so i missed out, and those shares still went up further. - spitting chips I was! He didn't offer to cancel the trade or anything. (This was with a reputable broker).