What's the state of private ad exchanges, today? "It's a disaster," Jeff Green, CEO of The Trade Desk, told OMMA RTB attendees on Thursday. Why? More or less, because of all the friction created by overprotective publishers. There's "more friction than liquidity," Green said. But, if publishers were going to be so protective of their ad inventory, why build an exchange in the first place? Blame supply side platforms, said Green. In recent years, he said, SSPs convinced many publishers that there was no downside (at least from their side) in launching their own exchanges. That said, what Green sees as a disastrous private exchange market is not, in his opinion, representative of the health of RTB. On the contrary, "RTB is doing phenomenally well," he said.