While I agree there are some people who just can't program, I think it's worth pointing out that in many cases, the candidate who simply cannot FizzBuzz in one

While I agree there are some people who just can't program, I think it's worth pointing out that in many cases, the candidate who simply cannot FizzBuzz in one interview, will do so (or other similar tests) perfectly well after a few interviews. Have you even blanked out on something you knew the day before the test? Most people have. Some (not all) of these interview bombs, are by people who know perfectly well how to program, but can't do it in an interview (until they've done a few interviews and get over that).