In other words, they have aspects of an email system, but they don't have a full offering. To me, the question about companies like Twitter is: Do they fundamentally evolve as sort of a note phenomenon, or do they fundamentally evolve to have storage, revocation, identity, and all the other aspects that traditional email systems have? Or do email systems themselves broaden what they do to take on some of that characteristic?
This rings incredibly true to us here at Posterous. We're positioned in a way make this exact thing a reality.
Exciting times, friends.