I need information on corporate structure, in particular, structure of
companies with many different seemingly unrelated divisions.  For
instance, Sony has Sony Music, Sony Pictures, Sony electronics, etc...
 Are they each separate companies held under blanket corporation or
just divisions, and what are the advantages/disadvantages to various
structures.  To put question in context, I have two separate
businesses and plan on starting more, each with different focus/brand.
 Sort of like an incubator, but business ideas/projects started are of
my own.

A sub-question to this that relates to the previous and I will award
an extra $25 tip if answered is information on 'modular' corporations
for lack of a better term.  I mean incubators/multi-industry companies
like sony et al that have divided their accounting, marketing,
customer service divisions into little self-contained modules and are
able to assist the many companies within the overall
incubator/corporation.  I read somewhere that a certain company
(forgot which) treats their internal IT department like a separate
consulting firm and actually gets charged/pays for services, even
though owned/part of corporation.  Can this system be applied to other
divisions (accountint,etc.) and used in incubator like environment. 
what are the advantages/disadvantages?


Thanks in advance!