Zero Hedge found some stock trades executed before they were placed. This happened during one second on September 15th. High Frequency Trading favors those with the fastest link, a few milliseconds offering an edge. It appears that the orders were in a slower queue than the order fills. Some Yahoo shares were sold 0.190 seconds before they were ordered as the time stamps prove. There wasn't an overload at the time. Does this mean delays are more common than thought? Is someone exploiting this "fantasecond", this make-believe gap in time to bypass price protection on bids?
Charts and details at Zero Hedge.