Some observations/questions: Take the example of Napster. The service was set up in a dorm room. When did Napster reach its GP? I would say, it was self-sustaining from day one. It was immediately worth joining and investing in (by installing a client and sharing one's own collection).

Napster is an interesting case. I would say that it is hard to unravel it as on one reading, the entire model was fraud - "stealing IP" - and on another reading, it never ever entered any economic systems space because it never ever generated and released any monetary value. So, as there was never any monetary value, there was never any economic calculation, and thus it never achieved sustainability on its own merits. E.g., it collapsed when faced with the obvious attacks.

Systems like Mojo Nation moved to bring economic calculation back into the business cycle. Systems like BitTorrent moved to take the usage model out of the business cycle (by being code / service only). Both and all other followers responded to the failure of sustainability of the original.

Of course, these observations are contradictory ;-) It is an interesting case...