I don’t think it’s rude at all, especially since I pretty much volunteered myself as an Example Prosopagnosic by answering your post (in first-person, no less).
I was born faceblind, so I don’t know what it’s like having a functional facial recognition processor. That makes it trickier to describe, since all I have to contrast it with are second-hand descriptions (which, in turn, were also tricky for them to make).
It’s not that I don’t see faces. That’s a common misconception. (To the extent that having any conception about prosopagnosia is common, though I think there’s been a lot of improvement in general awareness lately.) I just looked at my brother’s face, sitting over on the other couch, and it’s all there: pink-red lips, pale skin, nose, pimple, brown eyes, bangs. Thinking of that fresh memory, I can almost picture it. Sometimes, just for a moment, I can grasp it, but mostly the memory is blurred and lacking in detail.
(It feels perfectly natural, having it blurry like that. So natural that I didn’t even notice I was doing it until I read other prosos’ descriptions of it. There are hardly ever faces in my dreams, and that feels perfectly natural too.)
Note that my brother is one of the easiest people to picture. I’ve known him for all sixteen years of his life, and when you’re reliant on general object processing to recognise faces, experience with a given face counts for a lot. After knowing my friend Jacqueline for four years, I was able to successfully recognise her when I bumped into her in a mall*. I wouldn’t have been able to do that if I’d had less experience with her and her appearance. It took me about a year, maybe a year and a half, to reliably tell her two teenage daughters apart, but after six years of knowing them I’m not sure how I ever managed to have trouble.
(It’s good that they were teenage. Children are tricky. They change quickly, so by the time you’ve built up enough experience with one face to recognise them semi-reliably, they’ve gone and gotten themselves a different one. When my brother was six, I couldn’t distinguish him from the other boys in his Cub Scout den. I didn’t feel a sense of recognition at my own face in the mirror until my mid-teens, 2 – 3 years after my face stopped developing. (Even now, I can still tell which other faces I would have trouble distinguishing from my own, had I less experience with mine. Plus, I’m not entirely sure how much of the ease is due to my large glasses.))
If you want to read more, try looking through my prosopagnosia tag or dhalim’s blog. For another, very detailed perspective, Bill Choisser’s classic book, Face Blind!, is freely available on the Internet. (I haven’t read that book since I was first learning about prosopagnosia seven years ago, so I don’t remember at exactly which points my mileage varied. I do remember it being interesting, though.) The general prosopagnosia tag on Tumblr (which I track, and is how I found your post) sometimes has good stuff in it, though there’s also the occasional non-proso using us to make Profound Statements about Seeing People for Who They Are Rather Than What They Look Like and artworks depicting faceless people (see paragraph 3).
*Malls are tough. Absolutely anyone could be in the mall, so you can’t use context to narrow the list of potential suspects. (“She’s really tall and she’s at my Girl Scout meeting, so she must be Jenny, because Jenny is the only really tall girl in my troop.”)
I honestly didn’t expect such a brilliant and detailed answer. Thank you so much for the answer, and for your patience! You’re great!
And I’ll definitely take a look on the links you shared with me.
Brinens and Things 
