I can tolerate a person trading with a computer or a computer trading with a person but computers trading stocks with computers? That seems incredibly and obviously wrong to me or am I missing something here? Never mind my philosophical objections, I think it's just plain dangerous. If computers are trading with computers than they are all presumably using different proprietary algorithms. I would say that the algorithms, because they are different, will inevitably clash and have a cascade effect, possibly causing a market crash. The one day major spike down a little while ago was attributed to that by some but I guess the blame was shifted elsewhere. All it could take is for some selling to trigger another algorithms quirk, bad code or just difference and more selling and for it to cascade and you have a quick crash. If that happens guess who gets screwed? The infinitely slower human traders.