Just came across an interesting article on face blindness (a.k.a. Prosopagnosia), a subject that interests me because of my own difficulties recognizing people. It's very good, you should read it if you like Oliver Sacks-style articles about the nutty things our brains are up to, or if you're bad with faces. Oddly enough, they now say perhaps as much as 2% of the population has some degree of prosopagnosia. Which is strange because I almost never meet people who say they're bad with faces. But it sounds like a lot of people just fake it and don't even tell people. I have met two people who say they can't recognize people, though, so there are a few.