I doubt you or I are actually qualified to comment on whether the net externalities of HFT are positive or negative. You are incorrect that there are no positiv

I doubt you or I are actually qualified to comment on whether the net externalities of HFT are positive or negative. You are incorrect that there are no positive externalities. You might not care about your trades happening quickly, but that liquidity is what allows them to execute at a good price and also a part of what makes indexing possible. I totally agree on the wisdom of unsophisticated investors who think they can back test some "strategy" based on trends and support levels and so on and then actually go and make money. It's unlikely to work, they probably have no understanding of what their actual risks are (I'm talking probabilities, not just value at risk at any given time), and they are losing money on trading fees unless they can actually point to some competitive advantage they have over other traders.