Different Approaches to Recommendation

Pandora - technology is based on a deep structural analysis of music files. It detects subtle musical patterns, and organizes those patterns into groups, hence the ability to recommend other songs based on structure of initial song

Strands - technology in based on social behaviors. its goal is to personalize your online experience, by understanding who likes what, and generating suggestions based on the social feedbacks of users.

Aggregate Knowledge - Chris Law explained that his previous experiences taught him that the tastes of your friends usually poorly reflect yours. This is why they are more focused on analyzing the context of the visit (traffic source, landing page, semantics, visitors' demographics) and the behavior of the visitors.

to conclude, we have 3 different approaches:
- Pandora: deep structural analysis of an item
- Strands: intensive social behavior analysis around an item
- Aggregate Knowledge: structural analysis of an item, paired with behavioral analysis around the item

http://hyveup.tv/2008/10/3-different-approaches-to-automated.html