I don't think it scales, because I'm not sure it scales on private trackers already. I'm not deep into that space, but I think there's a lot of problems with it that will scale as adoption scales, particularly around policing the sale of invites - the hope would be it self-police through treebanning, but I'm not sure it does.

I think a sort of pseudo-anonymous auth system with backed in invites and treebans that website owners could easily adopt is interesting though. I'm not sure it's a business - for adoption reasons it likely needs to be a protocol - but it's an interesting idea, if it doesn't just turn into a huge admin headache for publishers.