only 10 kinds of people in the world

I first heard the saying "There are only two kinds of people: those who think there are only two kinds of people, and those who know better" about ten years ago* and I still tell it to people when I think they're lumping others together too broadly. (Apparently this quote is from Tom Robbins' Still Life With Woodpecker, which I read in high school, but it didn't stick with me then.)

Today, on a t-shirt, I saw the geek analog of the saying: "There are only 10 kinds of people: those who understand binary and those who don't." Too bad you can't say this one out loud.