Influencers in the online world
Robert Scoble has a note on how invisible influencers can drive interest in products. As I just started reading Malcom Gladwell's Tipping Point (four years after all connected people I imagine), I look forward to re-read Scoble's article when I've finished the book. But I think that one thing that makes the online world different with regards to influencers is the ability for a person to turn him-/herself into a de facto publishing platform at no (direct) cost. Regardless of channel (web, e-mail, IM) it is really easy and cheap to spread information in a way that cannot be described as truly one-to-one but rather one-to-many (publishing).