Sell Side Advertising.

Lately, I've been reading in a lot of blogs about the concept of sell-side advertising. I'm in an airport, so I can't reference anyone at the moment, but the concept is essentially that advertisers will post the creative for their brand. Eg, here's a 468*80 banner, here's a text ad, here's an email valid for a particular period. Here's what we're going to pay for a desired action (email registration, purchase, etc.)
Then publishers (traditional, web, blog, whatever) can choose to run it, while following the rules laid down by the publisher.
From the perspective of an advertiser, I think it would be great. There are always lots of intriguing places to advertise (so, we run ads after people submit resumes for zookeepers ) that for a variety of reasons aren't practical to try (to small of a market, not enough time to focus, lack of $'s).. In this model, the advertiser could let anyone test out the ad model.
There are a few models similar. Affiliate sites have long done this
sort of thing. Plus, you could argue AdSense can do this, but it's a limited role. I think there's the potential for a centralized,
distributed marketplace. Google does appear to have the lead here,
especially if AdWords moves just beyond keywords and text in its
contextual model.
It'll be fascinating to see the space evolve.