When I talk about "sell" I mean sell directly with a human touch. Like the way a newspaper or a network of radio stations has actual salespeople that sell ads.
It sounds like a service some company should step up to provide! Make the job of those salespeople easier.
Instead of selling "clicks" and "impressions", just sell the damn banner ad. The advertiser sets their budget and target audience, a few suggestions of websites where to run a banner for (x) days show up, the advertiser picks some of them. On the other side same story and the website picks which ads they want to run.
Many other models are possible.
I wonder why we don't have such competitors. Ah right, because Google abused its monopoly position. :-)
