[quantumstate]

Basically you cam imagine a market with only long term traders, there is a certain amount of money being generated by companies which feeds the profits of the market.

Now add some HFTs, these make a profit (there is empirical evidence for this claim). Now money is leaving the market without going to long term investors. Thus the long term investors are making less profit.

Now the big unsubstantiated assumption I have used above is that HFT adds no value to the market. I do not feel I am in any position to argue about whether this assumption is good or not. The above argument is presented in the hope that it makes things clearer and points towards what I think is the fundamental point which needs to be discussed: "Do HFT traders add value of a market?"