I've always known I'm terrible at visualizing. The first question from the quiz in the article is "Conjure up an image of a friend or relative who you frequently see". I chose my wife whom I see for hours each day. I tried to visualize what she looks like -- nothing. Is this really so rare?
I don't think I have a very difficult time visualizing things, but I seem to have a hard time describing what people look like. Whenever anyone asks what person X looks like, I always really struggle with the question and rarely give a useful answer beyond things like skin color, hair color, and sometimes height. I don't know why this is at all -- whether my visual memories (maybe of specific people?) are missing fine details, whether I'm just generally lacking in practice in describing people's appearance in words, whether I'm especially inattentive to people's appearance, whether it's a psychological block, or something else. (I don't experience face blindness; I can easily recognize and distinguish people when I see them in person.)
On the opposite end I remember every face I've ever seen (that has been put to a name). I remember most names and faces from each of my elementary classes including pre-school. Completely useless skill as I can't remember other things to save my life unless I read them 100 times over.
You can use it to pretend you know everyone in a party even though all you know is their face and name. :)