This was exactly what I was thinking. I suspect (I don't know of any data on this, but I'd love to see some) that there's a huge gap between users that sign up to a new service because they hear about it somewhere and think, "hey, that sounds neat, I want in first/I'd like to explore" and someone who's simply been paid to setup an account. cf. grassroots (http://en.wikipedia.org/wiki/Grassroots) v. astroturfing (http://en.wikipedia.org/wiki/Astroturfing)