Early adopters influence initial take up. Tumblr is way beyond this now. Once it's reached the high school kids, then it can't really be called "early" any more

Early adopters influence initial take up. Tumblr is way beyond this now. Once it's reached the high school kids, then it can't really be called "early" any more. They'll only move on once the service is no longer seen as cool, and the early adopters have - at a modest estimate - absolutely nothing at all to do with this.