Google's Thin Content War Rages On
Several reports emerged over the weekend (and into Monday) that Google initiated a manual action over websites offering up thin content.
Google relies on algorithms to evaluate and improve search quality, but does periodically take manual action on those websites that it determines use "spammy techniques" and will demote or even remove them from its search results (which seems to be the case here).
Google has not officially confirmed that a manual action took place, and many are suspecting it has more to do with some after effects of one of the other algorithm updaets (e.g. Panda).
There are a long list of reasons manual actions happen, from the appearance of unnatural links to the presence of thin content (which provides little or no added value). As you might imagine, those affected by this most recent round of manual action notices are claiming their innocence. While it has been suggested it could be a bug in the Google system, chances are excellent that it's not and that there was likely a perfectly good reason for the manual action.
Webmasters will be able to determine if they were affected by visiting Google Webmaster Tools, selecting "Search Traffic" from the dashboard and clicking manual actions. From there, any manual actions will appear.