Intense Debate is a sophisticated external comment system for WordPress blogs. From Automattic.
http://www.intensedebate.com
Widgets · Comment System
Get access to data on 21,728 websites that are IntenseDebate Customers. We know of 2,531 live websites using IntenseDebate and an additional 19,197 sites that used IntenseDebate historically and 1,514 websites in the United States.
Get a list of 21,728 websites using IntenseDebate which includes location information, hosting data, contact details, 2,531 currently live websites and an additional 701 domains that redirect to sites in this list. 19,197 sites that used this technology previously and 1,514 websites in the United States currently using IntenseDebate.