I'm reviving this old thread because during recent years, many links on face blindness or Prosopagnosia (aka Facial Agnosia) have appeared on the internet, including this article from medicine.net. The TV show "60 Minutes" also did a segment on being face blind.

Unfortunately, when a person does not recognize others society may chalk it up to a personality shortcoming such as a lack of interest in others, being unfriendly, cold, distant, or indifferent.

Here is a link to a current thread on Aphantasia, or inability to visualize. On that thread, several posters have mentioned face-blindness. It is possible that the two may be somewhat related; It describes experiencing an inability to visualize anything including faces, and how some compensate with other skills in order to recognize people.
Originally Posted by facebook article for original post in thread on Aphantasia
1. Can you picture my face?
No. But it’s not personal.

2. So you don’t know what I look like?
I know facts about the characteristics of your face. If you have radiant blue eyes, I may have stored that information. I know the “essence” of your face, but I’m unable to project it visually in my mind because there’s no screen.

3. So you don’t recognize me when you see me?
I do. Exeter’s MRI results suggest that the process of putting a name to a face can be separated from the process of mentally generating a face from a name. In programming parlance, I have a hash table.