monetizing social networks?

I saw a presentation in another class that identified a way to monetize social networks. The company is called Media 6 degrees (http://www.media6degrees.com/) and they have created an algorithm that identifies who your best friends are in facebook without collecting any private data. They then argue that a site that you visit (eg Reebok's website) would form the basis of a good re-targeting ad campaign for these friends (as birds of a feather flock together). So far, their results have been impressive, with all clients experiencing a significant increase in ROI!