Does any of this low-latency work make it back upstream into Linux or other parts of the software stack? As a latency-obsessed person I would love to know that the fruits of all this labor were available to me for my own low-latency systems. To me, that alone would be enough to feel that the latency-race is providing value to the world.
Also, one thing that was not clear to me is how electronic market makers make decisions. The article clearly states that they "have no opinion or information on whether Apple is a valuable company." So what do they have information about? The price history of the stock? The current contents of the book? And on what basis do they make decisions? I guess answering that question in too much detail would be giving up the "secret sauce," but I'd love to know even in broad strokes how an agent that knows so little can so consistently make money.