Ad networks use real-time bidding to auction banner ad space as the page loads. (I imagine that's part of the reason it can take so damn long for some news sites to load.) Why can't the user (or their user agent) take part in this same auction? If I'm will to pay $0.02 per page view on nytimes.com, but advertisers are only willing to pay $0.01 then I should be able to win the auction.