I have had a prosper lender account since May 2006. Although my net performance on prosper did not meet my expectations, I harbor no ill will at prosper or other P2P sites.
The section in my prosper profile under Why am I here? (unchanged since 2006) is now dated, but I still like the P2P concept. It's the unsecured part of the lending experience that I think is the achilles heel. At the time I joined, I'm not sure there was an easy way to change to a secured lending model, but I started lending anyway. I knew the risks of unsecured lending going in. And I'm not really surprised at the poor results/returns of the collective members.
Anyway... other than prosper, the vast majority of my lending and borrowing is secured. Seems like the way to go for me... and a secured P2P lending site could possibly be a good solution to help part of the US housing problem.