Actual value is what people are knowingly and voluntarily paying for your work. Front-running trades that were about to happen in milliseconds only produces "value" by exploiting flaws in the way the market clears. Muggers don't get to claim their income represents a contribution to society either.
Front-running is a loaded term (I'm sure you know that), and isn't what is going on in HFT - since front-running is illegal, and these programmers are paid to be on exactly the right side of the law.
