Prosopagnosia -- an almost unpronouncable word for a condition that makes every day life very difficult for its sufferers. A more descriptive term is "face-blindness" - the inability to recognise faces -- in extreme cases even those of your nearest and dearest. There is no cure, just coping strategies that vary in effectiveness.
It was quite a surprise a year or so ago when my brother announced he had this condition very severely -- none of the family had ever suspected he had this difficulty. Since he sent us various links to articles about the condition we all took the on-line test. My results came back as borderline as having a problem -- I just thought i was bad at remembering people!
Today he has been featured in the Guardian Weekend Magazine with an article on the subject in which he describes his difficulties: I don't recognise my own face . He has also written more about his condition on his website here: http://www.barryw.net/me/pa/prosopagnosia.html