Google recently gave details on its revised algorithm and unveiled some changes welcomed by those creating genuine websites.
One interesting revelation was the use of social media indicators as a means of gauging the true value of content.
Here are a couple of articles which go into some detail – well worth a read:
Google Forecloses On Content Farms With “Panda” Algorithm Update at searchengineland.com
Google’s Guide to High Quality Websites at the hubspot blog.