IMO, any p2p online lending is very very risky, no matter how much you diversify it. It is very hard for any independent party to verify the authencity of the documents submitted. With BTCJam, they do not do anything even if the user default, arbitration will not work unless the ID is correct and you live nearby the borrower.
We have many users who use arbitration when awards get issued. We're in the works of testing out more collections based services right now to strengthen this up so hopefully we'll have some updates to strengthen the consequences in the future.