An interesting post by Adam Veiner of Corante titled "Are Content Networks and Affiliate Networks Symbiotic."
 
What Veiner is engaged in is a practice called "Bouncing" or "Traffic Bouncing" - a perfectly legitimate means to generate additional revenue from a site in addition to what the site itself is producing from existing affiliate program relationships. Bouncing entails paying for visitors from a PPC network (in this case Google Adwords) to promote an affiliate program and then using strategically placed content ads in the hopes of garnering additional clicks and in turn revenue - literally bouncing visitors around until they find what they want via affiliate sites. Perfectly ethical method but one would have to question of the approach of using arguably the most expensive PPC network (Adwords) to bounce traffic. Another option may be to utilize second tier networks such as Miva, 7Search, Search123 or Enhance to drive traffic as the cost per visitor is exponentially lower which could result in an even higher return on investment if done correctly. A great post by Veiner and a viable online business approach (promoting affiliate programs through PPC and profiting from both the affiliate program and the content ads).