Fundamental flaw with Prosper is it is built around the securitization model. With the securitzation model, ownership of the note becomes so dispersed that no one effectively owns the debt. Thus the problem with see with collections.
Under the old concentratated ownership model, if a deadbeat defaults, the debt owner can go after the deadbeat aggressively because there is a minimizing losses financial incentive. Here, debt becomes a collective good so no one cares. None of us are going to go kneecap some deadbeat over $50. However, if the amount was $15K, that's a completely different story.