Nick Denton, founder of moreover.com, is starting a new venture revolving around the idea of making it easier to search for blogs (good idea). The plan would be ad-supported (bad idea).
Denton plans on mixing blogs and advertising. Advertising and blogs don't mix. Unless if you're "advertising" someone elses blog (Pyrads, Blogsnob, for example).
The way I bet it roles out, advertising gets distributed on this blog network, the network gets paid for advertising, maybe bloggers get a portion of the pay (in which case, this might work). Now, Denton's plan is vague, so I may be totally off the mark. But the fact that it sounds like a purely adsupported revenue model instantly raises my skeptisim.
Bottom line: Why would advertising a company's product or service resonate on anyone's blog? When a real voice is juxtaposed against advertising, the real voice wins and the advertising loses.
For info go here, here, here, here, here and here.