Very interesting article here, about the person that figured it out and how, it also shows you the value of a couple of milliseconds, that and some very fast programs to analyze trades.
Not only is this illegal, but makes you realize that the actual volume of shares being moved on the market is inflated, if you place an order for 100,000 shares of Apple and someone reads your order and places the same order milliseconds before you to turn around and sell you those 100,000 shares at a profit, well that's 200,000 shares in volume, without the intercept only 100,000 shares would have been moved.
Should be interesting to see what the Feds do about this.
http://www.cbsnews.com/news/is-the-u...market-rigged/