I admit that I know nothing about mainstream online marketing but my eyes were opened recently.

I ran into a site for... oh let's say... teddy bears (not really - just for the sake of this thread). The site was well SE optimized for people looking to buy teddy bears online. But no teddy bears were for sale on the site. Links to products didn't go anywhere, infact, none of the links worked on the site at all. The only links that actually worked on the site were for google adsense ads that were real merchants selling real teddy bears.

Multiply this formula a few hundred times and do you have a viable way to make some serious dollars?