worldwide

53,651 - "If we could get access to the usage logs of the top 10 Web 2.0 properties, I would bet that their 10,000 most active users would all be the same." - I'd guess that if you define a top Web 2.0 property in terms of user adoption that's not the case. The TechCrunch aware crowd might sign up the very first day a service launches but then quickly moves on without becoming an active user - just check alexaholic two weeks after a tc-review (it's just not possible to microchunk yourself into a few hundred pieces.)