These statistics about Twitter are fascinating. (Here's some additional analysis.) We see Twitter without the circle of fawning admirers, with her make-up removed, being herself at home. She still looks pretty good, without the hype and glitz.
The statistic that will appeal to the cynics and skeptics: 15% of the people who follow more than 2,000 people are social media marketers. Yeah, I kinda suspected that there were more than a few people playing the You Watching Me Watching You game.
The rest of the numbers are what you'd expect from a relatively new social media outlet, so there's no reason for Twitter to blush. Half of all users aren't active? A significant number of blogs are also inactive, dead, pushing up the daisies, rung down the curtain and joined the choir invisible. A minority of users create most of the activity? Not exactly a shockeroo. I'd be very suspicious of the numbers if they showed a different picture.
The most interesting statistic for me, as a hybrid social/computer scientist, is the take-off number of 150 followers. That's the threshold where people where you, and the people who know you, have a real network going. It's also where people who don't know start thinking you're worth noticing.
And for you product design wonks out there, APIs really matter. Twitter's success owes a lot to applications beyond www.twitter.com.
The moral: You don't need to claim that Twitter has changed the world, or that Twitter now overshadows all other social media, to believe that Twitter is a success.