There's a lot of FUD surrounding the topic of high frequency trading (lowercase). Much more important to stability and sanctity of markets is transparency and effective regulation. Traders by design are trained to find inefficiencies to exploit -- that's how they make money. If some traders have discovered that by having computers trade really quickly, they can get an edge - well, that's kind of the point of trading. I think this paper is right to point out that high frequency trading has little to no impact on the overall marketplace.