I’m going to make a partial stab at this: in-joke
There are two types in this world: Qwerty and Dvorak.
There are two types of people in this world: those that are wrong, and me. 
There are 11 types of people in this world: those who understand binary, those who don’t and those who laugh even if they don’t get the joke.
There are two types of people in the world, stupid and apathetic.
How do you tell them apart?
I don’t know and I don’t care.
ahem…
I believe it’s ‘sons-o-bitches’
Of which I am obviously one
There are two types of people in the word: those that probably believe in certainty and those that definately don’t.
There are two types of people in the word: people who think Michael Jackson is a complete loonatic and Michael Jackson.
But in many cases the point of the joke is that its a stupid division, hence might be wrong and not include everyone.
Originally posted by KP
B) " the reader has to be one of those people being described to get the joke"
Tautology: if there are only N types of people, then you must be in one of the categories if you’re a person at all.
Therefore I’d have to call them “jokes that are only for people”,
A) “one in which the writer is pretending to be one of the people they are describing”
Due to the tautology above, only a nonhuman could pretend to be one of the people described, so this subcategory is: “jokes by non-people”
These jokes only describe one of the groups, the other is the exclusive. For example the one with binary numbers, if you don’t get them, you don’t get the joke.
But I would like to know what these jokes are called. If there isn’t a term for them, what should it be?
What’s wrong with “2-kinds-of-people jokes”?
Not a joke, but fitting for the thread and timely to honor a great lefty:
“A pitcher needs two pitches, one they’re looking for and one to cross them up”
-Warren Spahn
died yesterday at age 82I love threads that draw in lurkers.
There are two kinds of posters, ones who do and ones who don’t.
Welcome to the Boards, Clare’s guy!
Smart-arse.
Whoops, that was a suggestion for the type of joke this is. I didn’t realise that we’d past page 1!
Well, then - the answer is obvious. It’s an N joke. 
Ahem… oddly enough, I have written a song on this very theme. A sample of the lyrics:
Two kinds of people in this world.
One says be what you want to be
the other says, be normal which is just like me
Two kinds of people in this world.
Type one thinks they know what’s best for you
I don’t think I ever met type two
etc.
By the way, the famous “TATKOP…those that divide the world into two kinds and those that don’t” is from that great humorist Robert Benchley.
Fifteen Iguana
There are tintypes of people in the world of photography.
Yep. Sure are.
There are two types of non sequiturs in this world: the kind where one statement does not logically follow another, and the other with big boobs.
There’s one type of person in this world, those who are surprised by… wait, there’s two types of people in the world, those who like Monty Python and…