People pay attention to the winner. But what about all of those other people bidding? Just because someone didn’t win an auction doesn’t mean that they’re not interested in doing business with you. And if you’re a publisher who is constantly selling inventory, after you strike a big deal with an advertiser, you can’t just always go back to the same buyer with your next big deal because they might not have the budget for it. But you got information that shows who is interested in you, even though they might not have cleared the last auction. A lot of that data gets lost or thrown out, but there’s a lot of value associated with it.