This is what I was going to post about. I am terrible at recognising faces. People I know well are fine, but even a quite good acquaintance in the wrong context can easily throw me completely. There are a very small handful of celebrities I can recognise by their faces. I recognise most people below the level of fairly-good-acquaintance by their voice, not their face. There have been many occasions on which I haven't realised I know someone, or have seen an actor in something else, till they speak.

It's also not quite that I remember the features but can't synthesise them into a face, which I think some people with this difficulty find -- I have real trouble remembering features, too. Half the time, if you ask me whether friend-so-and-so has dark or light hair, or is tall or short, I'll struggle to say for sure.

I think I'm relatively bad at reading facial expressions, too.