Large media companies have already recognized the increased demand for inventory that's priced for performance. They have created their own vertical networks, which provide significant reach. Given that most advertisers can't frequency cap across multiple network buys, the limited reach of a vertical network is preferable in some ways to your standard network buy that reaches 90% of the web. Also, a vertical network buy composed of one or two dozen major content sites provides much more inventory control than a "transparent" network buy of 60 or so sites, where ads may well end up running mostly on a handful of social networking properties.

In addition to vertical networks, direct sales forces will sell non-guaranteed "remnant" inventory on their site for prices similar to the ad networks. In this situation, cutting out the networks is a win-win for both advertisers and publishers. In my experience, this tactic is letting publishers to take revenue from the networks without cannibalizing revenue from brand campaigns.

Major publishers recognize the downward pressure on CPMs and and are now capturing the demand for inventory that is priced for performance. Not only are major media companies creating their own vertical networks, direct sales teams will sell non-guaranteed "remnant inventory" on their own site for a similar price to what the network is charging.

Most of the top 10 networks have high reach, BT, demo-targeting. I don't think media buyers can even tell a difference between the ad networks.

interCLICK offers some level of transparency. Tremor offers great rich media opportunities.

But otherwise, the only major differences between the top 10 ad networks are datapools and technology. Some have larger datapools to work with, others may have better algorithms.

But buyers don't really knows whose best. Each and every ad network just says they are but fails to back it up.

I'm not including affiliate and lead gen firms. Those are a different animals.

Low-quality advertisements may diminish the reputation of the publishers that run them. I think Gawker's refusal to use ad networks, in addition to having a unique non-corporate voice, probably garners advantageous CPMs and higher total revenues. Only they know if it works better or not. But the art used for unsold inventory certainly raises the value of the site in my opinion. I wonder if they've studied that.