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.
The implementation is lacking. For example you can invest, but once you do you can't cancel that investment. You should be able to cancel up until the loan is taken. That would prevent some scams.