You have computers pinching a penny from everybody, eventually the people have no money left, and the computers have penny by penny accumulated all the wealth. All the market will be left with is computers at war with each other trading back and forth with no human being. Also over time the liquidity in the market will decrease greatly, and it's liquidity that was never there to begin with because is was all in the name of trading, this could very well be the cause of the next market crash creating a massive liquidity crisis when the HFT stops, what will the volume and breadth of the markets be. Some say HFT accounts for 70% or greater of the trades taking place in the market today. Used in context of private placements, sweep trades and advanced schemes, it's outright fraudulent to use HFT. Something has to be done soon or the market will be doomed to the next bubble bursting, it's probably too late to prevent the next crisis, and regulators only act in retrospect after the damage was dealt. So sit tight and hold on for the wild ride ahead.