Whenever I think about complex topics in the social sphere, I always try to relate them to “real life” examples. So when I think about influencers (or advocates, which is not the same thing) I ask myself who are real influencers in the physical world. Because their digital counterparts are then easier to identify.
There are two major influencers in “real life”. Those who got the money, and those who got the political power. The equivalents in social are those who control or produce publishing and/or content (social currency), and those who control and/or manage community (social political power).
Draw your own conclusion but if you’re looking for influencers online, that’s where I would start.
Like Clint used to say, there’s two kinds of people in the world, those with loaded guns, and those who dig :)