I definitely have a mild form of this (face blindness) - I recognise people I am very familiar with, but if I only see them occasionally, or they are out of context, it's a problem. I totally blame my dad - he was just the same
I tend to remember people by hair or skin colour, whether they wear glasses or not etc. I worked for 10 summers at a camp for kids with disabilities - one of my duties was assessing the new staff and assigning campers to them - I had a terrible time remembering who was who, and usually had to hear them talk (we had alot of international staff)before I knew who they were. I never had the problem with the kids. With ds, I did notice once that in a soccer session, with kids he wasn't familiar with, that he would pair up with either the Asian or Hispanic kids (there were only a couple in the group of mainly blond haired boys) - maybe that was his way of being sure he remembered who his partner was ?
