(Although there is a problem if you want to make nice things and get paid for them...)
There already are P2P social network platforms, the problem is how do you get mass adoption?
The actual cost of what e.g. FB does for its users is tiny.
What the magnitude of such metric actually is, probably depends as much on cultural aspects of your target demographic as the quality and usefulness of the network provided services.
Surely there is an academic paper on the subject, but if there isn't, then the real question is Why?!
There are various ways to get it. I would say viral expansion is the best way.
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