prosper.com is it a good idea?

I find it incredible that people lend money to strangers ! I really do not know how such a “business” can happen and cannot understand how the idea to create a website like this could have come to the head of the funder ! I would personally feel very uncomfortable with lending money to people I’ve never heard of before and, on the other side, could never accept to borrow money from strangers. This may be a question of culture and I’m not sure it could happen outside the US.
I’ve not heard of sites like this, but I know some websites where people can just give things (books, furniture...) and take things in return, for free. This is also based on trust... but on another level.