I just read Flash Boys[1], which is a fun read, and explains how being faster than others really helps in making money (on the expense of all other traders).
Basically: If you buy stocks, the trade is executed on multiple exchanges. When the order arrives at the first exchange, it shows your intent to buy these stocks. If a HFT firm buy them at other exchanges quicker than your order arrives there, they know they can sell the stocks to you, and make (a tiny tiny) profit, at your expense.<p>1: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Flash_Boys" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Flash_Boys</a>