Google+ API functionality.
https://developers.google.com/+/
Widgets
Get access to data on 6,290,548 websites that are Google Plus One Platform Customers. We know of 1,469,536 live websites using Google Plus One Platform and an additional 4,821,012 sites that used Google Plus One Platform historically and 830,067 websites in the United States.
Get a list of 6,290,548 websites using Google Plus One Platform which includes location information, hosting data, contact details, 1,469,536 currently live websites and an additional 481,511 domains that redirect to sites in this list. 4,821,012 sites that used this technology previously and 830,067 websites in the United States currently using Google Plus One Platform.