Who Gets the Highest Ad Rates Online?

This "article" is in a horrible, Forbes-like, turn-the-pages-for-you presentation format. But, it's still an interesting read. My summary (knowing little about the ad world).... To get high CPMs, either (1) sell lots of eyeballs in one batch or (2) sell the eyeballs of people who decide to spend lots of money.

It's pretty hard to create The Economist from scratch, but is it possible to identify long-tail opportunities with niche demographics of influencers? And, if so, how would one go about selling his advertising space?