Want to see if you have face blindness or prosopagnosia? Go here and take a test. It won't definitively tell you, but might give you an idea.
I need lots of extra time to memorize just one face (like weeks or months). Until I finally get a face down, I rely heavily on hair appearance, clothing, if they wear glasses, skin color and things like that. I LOVE name tags, even though I'm pretty good with names. I just can't possibly memorize a roomful of faces in just a couple of hours.
This also means that, until I've seen a face repeatedly, all white people look alike, all black people look alike, all brown people look alike, all babies look alike, all thin white girls with long straight blonde hair look alike, etc. It's not an easy world for me to navigate. Hardest for me to distinguish? White men with brown hair. I swear they look like clones until I really know them well!