[yummyfajitas]

Flash Crashes also have no effect on the wider market. When you look at end of day prices for various stocks and indices, there is only a single symbol where you can actually see the effect of any flash crash:

https://www.chrisstucchio.com/blog/2012/flash_crash_flash_in...

Also, HFT lowers the price for people who do have information to trade with it. In this way, while HFT adds little information of it's own, it does enable better information transmission.

[Retric]

In other words in the short term can and will distort the market. So, the question becomes do they discover a economically meaningful price in the short term or is the processes essentially random.

As to lowering the price, arbitrarily increasing or decreasing the price is not an economically useful activity. The value of markets is price discovery, at best HFT reduce transaction costs though this is somewhat debatable as they are extracting money from somewhere.

[yummyfajitas]

You should read the article to see which symbol actually displays the effects of HFT shenanigans by end of day. (Hint: it starts with K, and it deserved everything it got.)

To see how cheaper liquidity directly enables speculators, read the section "Why Speculators Need Liquidity" in this post: https://www.chrisstucchio.com/blog/2012/hft_apology2.html An example is worked out in detail illustrating the point.

Also, HFTs are extracting far less money than the humans they replace. So if extracting money is what you want to prevent, congrats.