I think the worry about HFT is mainly that the value to society of adding liquidity does not outweight the cost of the money being extracted by these companies. It doesn&#x27;t feel like a good deal- it feels like we&#x27;re all being cheated.<p>The hard part about analysing whether is actually is good is in trying to figure out just what value we should place on added liquidity.<p>Can you explain why the value to society of the additional liquidity from HFT outweighs the cost (large profits to companies doing nothing else)? Not being facetious, actually interested in hearing your thoughts on it.