The industry is really good at direct response advertising online. The problem with vertical ad networks is that until you have engagement, integration, and proof of that consumer awareness, you are just going to keep devolving down to direct response pricing, which is sub $5 cost per thousand (CPM) for an ad.
We want it at the kinds of CPMs that supported the magazine and the cable industry, which is above $20, $30, $40, $50 cost per thousand. Advertisers will pay that once they feel like they're getting that value for it.
FYI: John Battelle co-founded Wired and wrote The Search, a pretty good book about Google, the history of search and the birth of the sponsored search industry.
He's also the founder of Federated Media, a gigantor online ad network composed of blogs like Dooce, Boing Boing and Ars Technica.
More Battelle on ad networks.