Additional businesses in this field:
Lookery profile similar concept uses public data to create user profiles

http://www.crunchbase.com/company/lookery

Optional Semantic APIs:
Peer39 http://www.peer39.com/
opencalais http://www.opencalais.com/

Advertising Aggregators:
247 real media NY http://www.247realmedia.com/EN-US/
Openad engine: http://www.openx.org/ (corrected)
Resolute Digital: http://resoluted.com/blogs/media/open-ad-servers/

May consider sezwho to find early adopter/influencers and base some advertising on their status updates

http://js-kit.com/comments/sezwho/

Implementation that bypasses where data comes from: Browser extension (that’s what zemanta’s approach has been)