Comment by carbon8

Parts of this post are premised the "influencer" marketing model, but there is at least some research indicating that it might not be as powerful as generally assumed. For example:

* http://misc.si.umich.edu/media/papers/wsdm333w-bakshy.pdf

* http://www.digitaltonto.com/wp-content/uploads/WattsandDoddi...

"Grouped: How small groups of friends are the key to influence on the social web," the book by Paul Adams @ Facebook (http://www.amazon.com/Grouped-groups-friends-influence-socia...), talks a bit about this.

Anecdotally, I've also seen quite a bit of evidence first hand that suggests the impact of influencers is not clear-cut.