Yeah, but I also think there's a kind of tension here, insofar as part of what makes Twitter a creative/productive place is that it manages to maintain a somewhat cohesive internal culture with its own set of social practices thanks (I think) to the relative difficulty it takes to join! I mean, maybe adding a cost of entry will create the necessary friction to ensure that only people who "get it" will join and stick around (this was always the theory for Something Awful), but it's genuinely a difficult tension to navigate and almost no one has been able to strike the balance well past a certain scale.