Thats one way to describe it.  Another way to describe it is &quot;hey prices at 2 different venues get out of whack some times, when that happens there is an opportunity to make money by bringing them back into alignment&quot;.<p>We don&#x27;t assume other kinds of middle-men require sleep aids when they do this kind of behavior (and in fact we usually encourage it), so I don&#x27;t know why HFT folks would need them either.