That's not to say that Facebooks ads won't work in some or most cases, but there are definitivly case where they are surprisingly wrong. For me personally I don't recall ever seeing an ad on Facebook where I felt that they where targeting me directly.
It might be that the only interesting piece of info about me is that I'm male and above a certain age. I would just think that given what Facebook knows about me they would be able to target my much much better.
Currently the company that does product targeting the best seems to be Amazon, but only in the books department.