All the usual caveats and complaints apply to this and most other network attempts: lack of standards, loss of local (or vertical) publisher control, network's taking too big a slice, publisher's taking too big a slice, wide variance in performance, too hard for advertisers to understand, too hard for account executives to understand.

If manufacturers, wholesalers and retailers can figure out complex distribution logistics for everything from packaged bacon to Hummers, why is it so hard for online publishers to figure out distribution logistics for a few bits and bytes?

What we have now is two major networks, Google and Yahoo, and Balkanization in the rest of the online world. There are people talking about and working on this to varying degrees, but it doesn't exist yet.

This starts to approach what I'm describing in local: http://www.registerlocal.com/