Cool, thanks. Personally, I'd like to hear a bit more about what you said in another comment here:

Just consider this a force that pushes the market towards efficiency and not toward inefficiency.

I have some doubts about this, because AFAIK, HFT often works in a way that is agnostic to the market itself. That is, the goal is to profit from predicting price fluctuations, and this might have little to do with reflecting market conditions. It would seem if you could manipulate the market with some trades, and then profit from that manipulation in others, that would be an approach that would be superior to predicting the market or getting reliable advanced signals of market movement. In that case, this could actually make the market less efficient.

EDIT: Another thought came to me: Is more efficiency a good thing anyway? I can imagine that some inefficiency between market changes and stock prices could actually be beneficial for the health of the economy. Inertia is a stabilizing factor of many systems.

And, even if we were to decide that increased efficiency was a goal, then we would have to determine what that efficiency was being measured against. If it's measured against news of market conditions, then to the extent that the news is biased or inaccurate or inefficient, then to that extent the market is modeling the wrong thing. I guess I see HFT as a possible creator and amplifier of noise. If news was most correct at time x after the first report, then slowing trading to that time scale could actually improve the market's efficiency.