Klout and Why the Design of Social Networking Matters : The New Yorker
Eric Barker stashed this in Klout
"Obsessive people are essential to sites like Facebook and Twitter. They add energy and buzz. Their identities get tied up with their avatars, and that in itself makes the sites seem important. They provide much of the content. A study published last fall reported that twenty thousand users on Twitter provide half of what’s read there."
Every network has people who are responsible for most of the interesting activity.
Communities coalesce around such people.
I agree with the New Yorker that assigning a number to represent someone's worth as an influencer is both clever and annoying.