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 10,510,581 websites that are Twitter Platform Customers. We know of 2,000,001 live websites using Twitter Platform and an additional 8,510,580 sites that used Twitter Platform historically and 1,139,393 websites in the United States.
Get a list of 10,510,581 websites using Twitter Platform which includes location information, hosting data, contact details, 2,000,001 currently live websites and an additional 2,334,239 domains that redirect to sites in this list. 8,510,580 sites that used this technology previously and 1,139,393 websites in the United States currently using Twitter Platform.