Aggregate Knowledge - Powerful Recommendation Engine

Chris Law is the co-founder and CEO of Aggregate Knowledge, a web startup specializes in serving recommendations on medium and high-traffic site.

Social graphs are poor predictors for advertiser is the major he learned from this startup.

Aggregate Knowledge doesn't tap into social graphs to serve recommendations to its visitors. Instead, it uses a complex algorithm that analyzes two major dimensions of the visitor:
1. Behavioral patterns
2. Contextual patterns

http://hyveup.tv/2008/10/introducing-aggregate-knowledge.html