Google+ API functionality.
https://developers.google.com/+/
Widgets
Get access to data on 6,276,603 websites that are Google Plus One Platform Customers. We know of 1,317,474 live websites using Google Plus One Platform and an additional 4,959,129 sites that used Google Plus One Platform historically and 729,718 websites in the United States.
Get a list of 6,276,603 websites using Google Plus One Platform which includes location information, hosting data, contact details, 1,317,474 currently live websites and an additional 575,715 domains that redirect to sites in this list. 4,959,129 sites that used this technology previously and 729,718 websites in the United States currently using Google Plus One Platform.