Fred Wilson talks about John Battelle's "new" idea for sell side advertising.
It's been around for a lot longer than you might think.
Commission Junction is one example (using affiliate links) but back in the old days (7 years ago) there was a lot of movement in this area as well.
Here's how I see it:
1. Advertising in a new medium is sold, not bought. It's not a commodity, it's an idea that gets sold to someone who wasn't planning on buying.
2. Google turns advertising into a commodity, because it's easy to measure and easy to buy. Once you get hooked on it, you want more.
3. It's not just the click, of course. It's the conversion.
4. Which means that there's room for middlemen who will optimize clicks AND conversion for advertisers willing to pay.
And that's where the future lies, I think. Something that's a cross between what Fred's talking about with www.cj.com. A whole cottage industry of people who figure out how to turn adwords into clicks into conversions.
Turning this over to outsiders is a little like using a rep firm to be your salesforce. You can do it, but to really win, you've got to do it yourself.
If it were me, I'd start a few competing groups within my organization and challenge them to "buy" customers as cheaply as possible. Cheapest group wins. If you get good at doing it in house, go ahead and start taking on clients!
And I'll finish by reminding you of my biggest rant on this topic: conversion skills are worth ten times what clickthrough's worth.
Link: A VC: Sell Side Advertising.