Create Facebook comments box as well as adding the comments to the sites own database.
http://wordpress.org/plugins/seo-facebook-comments/
Widgets · WordPress Plugins
Get access to data on 23,817 websites that are SEO Facebook Comment Customers. We know of 1,396 live websites using SEO Facebook Comment and an additional 22,421 sites that used SEO Facebook Comment historically and 854 websites in the United States.
Get a list of 23,817 websites using SEO Facebook Comment which includes location information, hosting data, contact details, 1,396 currently live websites and an additional 377 domains that redirect to sites in this list. 22,421 sites that used this technology previously and 854 websites in the United States currently using SEO Facebook Comment.