As a poster, I mostly agree with pageoneresults' first post, but I think you could be a touch more aggressive and it would be fine. But, between posts and in posts? Noooo...
But, his point about an adnetwork is also worthwhile. (I've posted on this several times before, this is the first time I've gotten to make this point using a real world example.)
I would look into having some conversations with industry leaders about sponsoring entire sections. Make it clear they will be seen as sponsors only, but they will have these pages to themselves. Then price it aggressively.
WW is populated with opinion leaders in industry. If you are, say, Bing and you're really, really trying to get market share from G, then an investment in ads on WW would be wise to keep the buzz on. An advertiser who has a service that delivers video to websites should be here they really trying to break into this brave new world everywhere. Afterall, you want the people on WW to have at least HEARD of you. Duh.
If the adnetwork were to focus on webbiz-related sites, well, OK, I guess. But, that's problematic.
All of this assumes that WW has a good numbers. They don't have to be GREAT numbers, because WW has a high-quality, very desirable audience that spends money and also influences others on what they do, on this site and in the real world, both. I feel fairly certain that WW does well, however.
But, on Foo, maybe, I'd run Adsense down the right side. Just to see, ya know. (Pageoneresults: "nooooooo!")
(Obvious point and a tip: 1. Selling and maintaining ads like I described is a full-time job for someone, maybe two someones. 2. For an ad server, Openx "Community Download" rocks because it's on your server.