We see Google has changed its search algorithm again today. Its interesting that they say the change is subtle and only affects 11.8% of their searchs. By my reckoning that a lot of search content.
The main change is around reducing popularity of sites that are not great content and contain lower quality text. I fully commend Google on this as webscraping and low quality content has certainly been on the increase in the last few years.
The change has only just been released in the US (Google.com) and they will roll it out across the world following review of the impact on US search results.
For the official release on the update visit Google Blog.