Where are SEO related service sites (e.g. backlinks, buy likes) advertising?

Given that Adwords does not allow for most of this type of advertising what advertising networks (other than the obvious, Adcenter) are Seo service providers and the like using to advertise? Any success stories or favorites? Seems most of the threads in this section address the other side of the equation – selling ad space on their own site.
Appreciate any insight.
Thanks!
Kermit

See original post by KermitIII