It reduces the bid/ask spread if there are more bidders and askers all doing their thing all the time: http://www.tradersmagazine.com/news/hfts-spreads-credit-s

It reduces the bid/ask spread if there are more bidders and askers all doing their thing all the time: http://www.tradersmagazine.com/news/hfts-spreads-credit-suisse-110365-1.html http://www.tradersmagazine.com/news/hfts-spreads-credit-suis... This part is actually a good thing. That said, I remain gobstopped that HFT is such a whipping boy in a world where no one responsible for the 2008 crash has been prosecuted or jailed. The incident here seems to either be a clocking artifact or an excellent exploit of a momentary inefficiency in the market - just the sort of thing traders spend their careers on hunting down and exploiting - so why... so... serious???