We are getting reports from across the SEO forums that Google has done another toolbar PageRank update. The update seems to be, once again, hitting sites that sell or buy links. Many are seeing PageRank drops to a flat out zero score, but some are seeing the typical reduction of 3 or 4 points in that toolbar PageRank score.Here are the threads discussing this now:Another PR downgrade today!, Search Engine Roundtable Forums
Why is my PageRank 0?, DigitalPoint Forums
PR4 to PR0 overnight penalized?, WebmasterWorld
Index Page not in Search Results anymore PR6 to PR3, WebmasterWorld
I’ll keep tracking the forums for more reports and add to this article.The main thing here is that there are two things here. The first is just a visible toolbar PageRank reduction and the second is a true penalty where your site is delisted from Google. Two very different things.