With everything that I think I know, I don't like firms being paid by the exchange to trade. I think it goes against the central tenant of an free and open exchange. Using the available technology to one up your competitors, of which, we all are, is what capitalism is all about. You could become a broker dealer, gain access, and place your servers at the exchange if you had the physical and intellectual capital to do so. So, in that regard, I don't think I have a problem with the strategy. There are hundreds of such firms competing against each other for your order and to game each other. But, I may be mistaken on this, specialists or market makers were never paid by the exchanges. I can conceive an argument that the rebate lowers the margin for the HFT traders and can therefore offer narrower spreads, thus, in theory, reduce transaction costs for the public. However, I don't think that is what is happening in practice.