[TheAlchemist]

Because it's not explicitly forbidden ?

I would argue that HFT is a rather small space, albeit pretty concentrated. It's several orders of magnitude smaller in terms of energy wasting than Bitcoin.

The only positive from HFT is liquidity and tighter spreads, but it also depends what people put into HFT definition. For example, Robinhood and free trading, probably wouldn't exist without it.

They are taking a part of the cake that previously went to brokers and banks. HFT is not in a business of screwing 'the little guy'.

From my perspective there is little to none negative to the society. If somebody is investing long term in the stock market, he couldn't care less about HFT.

[musicale]

Buying and quickly selling a stock requires a buyer and a seller, so it doesn't seem like an intrinsic property that real liquidity would be increased. Moreover, fast automated trading seems likely to increase volatility.

I tend to agree that for long term investment it probably doesn't make a huge difference except for possible cumulative effects of decreased liquidity, increased volatility, flash crashes, etc. Also possibly a loss of small investor confidence since the game seems even more rigged in a way that they cannot compete with.