Hacker News Reader

This isn't a definition of front running that anyone in the industry uses.

As you say, this is just arbitrage on public information. Latency arbitrage has been occurring for the last 200 years at least, it's an inevitable outcome of any system with multiple, geographicly separated markets.

P.S. I read Flash Boys. It's not very good.

This hypothetical HFT firm is part of "the rest of the market reacting"

They just happen to be the first among all participants to react. Why is that bad? Somebody has to be first

Perhaps I have misunderstood what front running is, but I have always thought it is really only applicable when you have an obligation to your clients to give them good execution. You can't front run a market, just your clients. An HFT has no clients on behalf of which they are executing trades, they are just trading for their own account.