High-Frequency Trading Is Good--and Evil

As Justin Fox points out, for as long as people have been trading stocks, there have been middlemen taking a cut of the action. Now, that cut has gotten smaller as markets have gotten bigger and more technologically-advanced, but it's still there. It's the implicit fee that intermediaries charge for making sure there's a buyer for every seller, and a seller for every buyerâ??for "making markets." But there's a new kind of middleman today.