[tptacek]

There are hundreds, probably thousands, of little exchanges nobody has ever heard of. Why set one up to "combat HFT"? Because if you can convince companies to trade on it based on nebulous "anti-HFT" features, you can collect fees without having to compete with the major exchanges, who both bid prices down and also have a 100:1 advantage in engineering and support staff.

Believe it or not, that's not even the "cynical" answer.

[minimax]

There are about 40 active registered ATSs for trading US equities. It's a high number but it's not thousands.

[tptacek]

There are many multiples more private exchanges, trading all sorts of electronically tradable instruments. I wasn't referring simply to stock exchanges. I was making a point about the return on investment you can get from developing a trading platform.