I have invested in some loans on this site.  Only 1 of these has paid in full or kept up to their payment schedule.  One of these had many repaid loans , so that is not garantee that the person is going to pay back.  When someone does default, you either take then to court yourself or lose your investment as far as I can see.

I also invest in a site called funding circle which, when someone defaults, has a part of their organisation which chases debt on the lenders behalf.  I have never had a problem with the latter.

I would love to invest in people via BTCJAM again, but as there is no comeback on people who do not pay....I can`t see its recommended.

Of course, if you do your due diligence, (as I clearly failed to do) then investing isn`t a good idea anywhere.