After a 4-1/2 month gap, Google launched another Penguin update. Given the 2.1 designation, this was probably a data update (primarily) and not a major change to the Penguin algorithm. Late Friday afternoon, Google's Matt Cutts announced on Twitter that they unleashed Penguin 2.1.
In short, Matt Cutts, Google's head of search spam, said it impacted about 1% of search queries.
Looking at the hundreds of comments on our quick post from Friday and looking at the threads out there in the webmaster and SEO communities, it seems like many many webmasters were impacted by this update.