[blumkvist]

Clicks are nice and a lot of people focus on them, but it's not a viable option for a lot of publishers/industries. Brand advertisers are about sending messages rather than driving traffic to pages and converting people there. Around 70% of display advertising is not direct response orientated.

The typical adnetworks give you ad tags which you put on your site and the ads are served from their ad servers. Then there are a few companies [1][2][3] that are marketplaces faciiliating transactions between publishers and advertisers, but they still use their own platform to serve the ads. And then larger buyers give them adtags, served by their own servers. Nobody in their right mind will just wire you money for ad inventory and just take your word for the traffic unless you are a very large name and have a proprietery self-serve platform (AOL/yahoo style). And even on these platfroms a lot of advertisers still use their own adtags (a recent java malware attack through yahoo's network comes to mind).

[1] buyads.com [2] buysellads.com [3] blogads.com

PS: sry for typos and formatting, on the phone atm.