Years ago I read (in a business book, I think) a compelling thesis
that 150 employees is the threshold size at which an organization
starts to lose its cohesive identity or unity, and that therefore it
is a good idea to create divisions or otherwise establish separately
defined business entities to maintain group identity, common goals,
etc. I need someone to refer me to the work and author. I'm pretty
sure 150 was the number.

Dear shikibobo-ga,

I answer this with a little trepidation as you say you read the book
years ago. The one I have found was first published in 2000. I hope
this is the book to which you refer. If it is not, then do ask for
clarification of the answer.

In 1993, Robin Dunbar, Professor of Psychology at the University of
Liverpool published ?CO-EVOLUTION OF NEOCORTEX SIZE, GROUP SIZE AND
LANGUAGE IN HUMANS?. Part of the paper looked at group size in humans.
The paper appears here.
http://www.bbsonline.org/documents/a/00/00/05/65/bbs00000565-00/bbs.dunbar.html
This is his home page.
http://www.liv.ac.uk/www/evolpsyc/dunbar.html

Others reading Dunbar?s paper interpreted the maximum number for group
cohesion was 150. This became known as ?the Dunbar Number?. This was
later taken up by a number of business writers. The below is an
extract from a blog called ?Life With Alacrity? where the author
discusses the Dunbar Number in great detail and refers to a number of
books in which this theory is mentioned. In the quoted paragraph I
have noted under each book the relevant amazon.com link where you will
be able to use the ?search inside? feature.

?This number of 150 has become "Dunbar's Number" and has been
popularized by various very popular business books such as Malcolm
Gladwell's The Tipping Point: How Little Things Can Make a Big
Difference (summary),
http://www.amazon.com/gp/product/0316316962/ref=ed_oe_h/104-1357398-6069554?%5Fencoding=UTF8
Duncan J. Watts' Six Degrees: The Science of a Connected Age (review) 
http://www.amazon.com/gp/product/0393041425/ref=pd_skotostech-20/104-1357398-6069554?n=283155
and Small Worlds: The Dynamics of Networks between Order and
Randomness (review), and Mark Buchanan's Nexus: Small Worlds and the
Groundbreaking Science of Networks (review),
http://www.amazon.com/gp/product/0691005419/ref=skotostech-20/104-1357398-6069554?n=283155
the ideas from which are the foundation of the various Social Network
Services that I've discussed elsewhere in this blog.?
http://www.lifewithalacrity.com/2004/03/the_dunbar_numb.html

I believe the book you are seeking is The Tipping Point: How Little
Things Can Make a Big Difference by Malcolm Gladwell's. Here is a
short extract from a review of the book.

?Interestingly, Gore Associates, a privately-held, high-tech firm in
Delaware has come to the same conclusion about size. At Gore, there
are no titles and instead of bosses, there are sponsors who are
charged with looking after the interests of those they are sponsoring.
There are no organization charts, no budgets, no strategic plans.
Salaries are determined collectively. They are also highly successful,
profitable and growing rapidly. Bill Gore, the late founder, stumbled
onto the ?Rule of 150,? stating, ?We found again and again that things
get clumsy at a hundred and fifty.? So 150 employees per plant became
the company limit. ?
http://www.thinksmart.com/mission/book_reviews_wycoff.html

?In large corporations, Dunbar found numerous examples that the
dividing line between a small and large business seems to be at around
150 employees. Businesses that are larger than this begin to run into
communications breakdowns and require formal procedures for conducting
business transactions.?
http://www.evoyage.com/ManInTheMist/ChapterFourMist.htm

All other searches on this subject come back to Gladwell?s book so I
believe that this is the book you are seeking.

I hope this answers your question. If it does not, or the answer is
unclear, then please ask for clarification of this research before
rating the answer. I shall respond to the clarification request as
soon as I receive it.
Thank you


answerfinder


"maximum size" "150 employees"
://www.google.co.uk/search?hl=en&q=%22maximum+size%22+%22150+employees%22&btnG=Search&meta=
"maximum size" "150 employees" dunbar
://www.google.co.uk/search?hl=en&q=%22maximum+size%22+%22150+employees%22+dunbar&btnG=Search&meta=

That's it. I knew I had read it around 2000 but I did not remember
whether I had been reading a new book or old book, or even a book for
that matter, so I did not want to bias your answer.