The page embeds the Twitter platform in one method or another.
http://twitter.com/about/resources
JavaScript Libraries and Functions · Social SDK
Get access to data on 9,851,156 websites that are Twitter Platform Customers. We know of 2,144,221 live websites using Twitter Platform and an additional 7,706,935 sites that used Twitter Platform historically and 1,208,139 websites in the United States.
Get a list of 9,851,156 websites using Twitter Platform which includes location information, hosting data, contact details, 2,144,221 currently live websites and an additional 2,093,330 domains that redirect to sites in this list. 7,706,935 sites that used this technology previously and 1,208,139 websites in the United States currently using Twitter Platform.