There's a passage in a book which I *think* is by Kurt Vonnegut that
talks about the minimum group of people to make a successful idea:
Type A people are geniuses who have ideas; Type B people pick up ideas
and can explain them; Type Cs have social weight to say "Listen to
these people!". A successful idea requires each of types A, B and C.
(It parallels some ideas in The Tipping Point, but I'm pretty sure
this is a Vonnegut thing.)

My question: In which book or story is this?

I am confident that you are remembering a passage from Kurt Vonnegut's
novel "Bluebeard."

Here are excerpts from two newsgroup posts that provide an apt
description:

"Catching up on some reading which had gotten by me I came across a
passage in Vonnegut's Bluebeard wherein one of his characters
(Slazinger) has written a book titled "The Only Way to Have a
Successful Revolution in Any Field of Human Activity."  Supposedly
extracted from a study of history this 'only' method requires a team
of 'mind openners' to break people out of their current mindset,
regardless of how unrealistic or dumb that mindset may be.

This team of 'mind-openners' consists of three people:

1)An Authentic Genius: a person with seemingly good ideas not in
general circulation.  He adds "A genius working alone. . . is
invariably ignored as a lunatic."  (copywrited in 1987)

2)A highly intelligent person in good standing in the community who
will stand up and attest that the genius is not mad.

3)A person who can explain anything, to anyone."

"Vonnegut then distinquishes between the types of men of words
necessary: 1) genius or original thinker, 2) one of public standing
who will more or less 'second' the original thoughts as having
validity, and 3)an explainer or person with the common touch who can
make new ideas understandable to all."

Posts to alt.fan.unabomber newsgroup
http://groups.google.com/groups?hl=en&lr=lang_en&ie=UTF-8&oe=UTF-8&newwindow=1&safe=off&th=6f3b002ca5341439&rnum=1

My search strategy was greatly simplified by the fact that I
recognized "Bluebeard" as the source from your description. I located
the newsgroup post cited above with the assistance of the Google
Groups search engine, using the keywords "vonnegut" and "bluebeard."

Unfortunately, my copy of "Bluebeard" was dismembered a few months ago
by one of my dogs, so I cannot give you a page citation. If this is
not the book you're thinking of, please request clarification, and
I'll be glad to put my thinking cap on and try again.

Best wishes,
pinkfreud

Bingo! Many thanks.

Thanks for the five-star rating and the nice tip!

~pinkfreud

Btw,

A search on scirus.com will find you pleanty of empirical support for
this literary assertion, if your interested. It is a common finding. I
suggest combinations of

diffusion of innovation
early adopters
core
periphery

as your keywords.