Market stabilization/liquidity is the effect that HFTs are supposed to have. If they didn't have a benefit they would have been banned long ago. And arbitrage

Market stabilization/liquidity is the effect that HFTs are supposed to have. If they didn't have a benefit they would have been banned long ago. And arbitrage is always zero-sum: when your purchase of an asset drives the price of that asset up, there is a finite maximum on the number of shares you can buy without driving the price up so high as to not be profitable. There is also a finite number of shares out for bid at any given time; if you buy all of them then there aren't any for anyone else to buy.