Prosopagnosia, in this case (link kindly stolen from Dubious Quality). This is really amazing. I'd heard about it before (being a psych major), but I had only heard about it occurring in victims of strokes or hypoxia. I had even read the book that they talked about in this article, The Man Who Mistook His Wife For A Hat. Still, the fact that it occurs naturally is really amazing. Now, if they could only do something for people who can't remember names. Damn you, you people and your names!