I love the basic idea of btcjam(providing capital directly from those with it to those who need it) but I think the implementation is really lacking a lot. As I said previously I doubt that most of these loans are within the usury limits(at least for US residents) and if that is the case there is some case law examples which would make me really nervous as an investor investing in high interest loans like that.
I think that the site should have some more security features, there is lots of verification that the users have to go through, but some of this can be faked, and if the user defaults the site doesn't really do anything about it. There should be an insurance option or they should add some more security features, like confirming bank account.