If you sign in to the Google webmaster tools site to check your Google rankings and site analytics, you will see a request from Google to fill out a detail form telling them which sites are BUYING and SELLING links. Perhaps their spam team will analyze that site and ALL of the links on it, then penalize everyone. They may even go so far as to trace what other backlinks those suspicious sites have and then penalize them too. This may account for why many buying sites suddenly dropped off completely in rankings overnight - and many selling sites suddenly loss PR or even got banned http://blogoscoped.com/forum/125191.html