Google came out with the Google Panda Update in April, 2011. Since then Google has come out with many other updates around the Panda update. Panda was supposed to fight content farms, sites that have a lot of duplicated content that were manipulating Google’s algorithm. Many large sites got hit like ehow.com. The newest update targets websites that are over SEO’d, so websites that have been optimized too much to try to get page 1 Google rankings. The video below explains this in more detail.