If the person believed a natural counterparty would come along within milliseconds, why would he or she enter a market order rather than a passive limit order?<p>There are many high-frequency strategies, and front-running/manipulating markets might be one that unscrupulous firms engage in, but most would rather make legal money.  The linked article doesn't make a lot of sense.  For one, flash orders are no longer available on major exchanges, and secondly it's very difficult (and costly) to push most stocks 30 cents away from their fair value.<p>Most of the anti-HFT things I read are pushed by buy-side traders who have a hard time tricking the market into executing huge orders without moving the price, as if they ever had some natural right to do so.  Trading is a competitive endeavor.  If your poor execution algorithm shows your hand and someone more sophisticated notices, it's fair play for them to use that public information.