If you have bought so-called “clean” links that pass PageRank, you might want to take a closer look to see if those links are still actually clean and that you haven’t been penalized for it.
Google’s Distinguished Engineer Matt Cutts reports that they have taken action today against several thousand link sellers that were passing PageRank.
Word hasn’t come out yet which network was the one penalized yet, or if it was a private in-house link network.
Judging from the wording of his tweet, it sounds as though manual action was taken against the link sellers, rather than an updated algorithm designed to target specifically these kinds of link sellers. That said, I fully expect they will be working on automated detection for these types of sellers.
This seems to be part of the link devaluing Cutts talked about in his “What to expect” webmaster video earlier this week.