Google annotates search results with social data, especially from Google+ and Google +1. Sometimes you may see on search results a page was mentioned in a Blogger post or a Twitter message by your Google+ friends. And, Google also lists the Google+ friends that +1'd the pages.
When a page has a lot of +1's, Google shows the number of +1's bellow the search snippet.
Now, to make the annotation more relevant, Google has started showing the number of +1's from your geographical location. For example, "763 people in New York, NY, USA +1'd" Google's Webmaster Tools page.
Below is the simple +1'd annotation:
Screenshot with geo location: