Form Google Webmaster: When we introduced the +1 button in March, Google search took a small step in an important direction. Search results can be more helpful, and more personal, when recommendations from the people you trust are there to guide your way.
The +1 button can help publishers, too. As potential visitors see recommendations from their friends and contacts beneath your Google search results, you could see more, and better qualified, traffic coming from Google.
Since we announced +1, we’ve gotten lots of requests from Google search users and webmasters alike for +1 buttons in more places than just search results. That’s why today we’re making the +1 button available to sites across the web. Sometimes you want to recommend a web page after you’ve visited it. After all, how do you know you want to suggest that great article on Spanish tapas if you haven’t read it yet?