I agree with jamiep on this, I've used air stones/air pumps in the sump, prior to any bubble traps/baffles before, just for added oxygen and for kicks. But you stick on in the display, the flow in a reef tank needs to be high enough that an airstone just really isn't going to be good, the higher current will just blow them bubbles everywhere. And as Global mentioned, if you have dead enough spots for an airstone to operate without causing bubbles to get everywhere, then you need more flow.
For a Fowlr, or fish only, sure I can see them coming in handy, just not in a reeftank. Besides, you remember what the air bubbles did to that poor yellow tang in Finding Nemo? So sad to loose ones marbles like that.