On the positive side, such system could help producing symbiotic relationship with new projects. P2P has for example been discourage because of the damage it could cause to the performance in the network. However, with an enforceable share ratio system in place, you could make sure P2P contributed as much as it used.

And with more users, the privacy is increased. That said, incentive schemes are famous topics for sociology and economics research, so there is validity in being careful.