Press Release Sites See Huge Drop In Google Ranking After Panda 4.0

Couple Of days Ago I reported at Search Engine Land that Panda 4.0 may have hurt press release sites and showed SearchMetrics data for PRWeb, PR Newswire, BusinessWire and PRLog all losing between 60% to 85% of their SEO visibility.
This drop seems to have come right after the Google Panda 4.0 update. The controversy around press release sites were mostly about links flowing from those releases, not necessarily the issue with the duplicative nature of that content. But let's be honest, many many press releases issued are content thin and spammy on the content end, not just on the link end. So maybe, just maybe, Panda 4.0 adjusted for it and the big sites felt it?
Sean from SEER also documented the drop via SEM Rush data and screen shots of before and after rankings for some press releases.

Google Begins Rolling Out Panda 4.0 Now

Google’s Matt Cutts announced on Twitter that they have released version 4.0 of the Google Panda algorithm.
Google’s Panda algorithm is designed to prevent sites with poor quality content from working their way into Google’s top search results.
But didn’t Google stop updating us on Panda refreshes and updates since they are monthly rolling updates? Yes, but this is a bigger update.
Panda 4.0 must be a major update to the actual algorithm versus just a data refresh. Meaning, Google has made changes to how Panda identifies sites and has released a new version of the algorithm today.