One thing that baffles me about Pay Per Post is it's business model. Is it an advertising company or a link service? PPP has companies come to them in order to get bloggers to write about products and set links up. One of the basic laws of the internet is the more links you have to your site, the more search engines will find your site. I venture to say that it is a link service.
In essence I guess PPP is both. I don't know how many people who read blogs really go to the advertised sites, but I do know that with all the links there will be a lot more people to find the companies through search engines.