Here's a real interesting comment from Mobius that he posted several years back that may be worth highlighting.
HFT is not what most think it is. It's not manipulating your price. It's trading the arbitrage in what you are willing to pay and what someone else is willing to sell for. There are tens of thousands of programs in the market every day and hundreds of different types of programs too. Some are arbitrage, some are sell side only; some are buy side only. Many 1000's are from retail traders running automated trading. There are more retail automated programs by far than commercial these days
There are many types of HFT. A lot of HFT volume (most?) is market makers balancing the order book and making money on spreads. There is no room for statistical arbitrage on the retail side. - those easy pickings were picked long time ago with the rise of computerized market makers like citadel