I am sorry this thread seems to have occurred mostly during the ALI-
ABA (American Law Institute Institute-American Bar Association) meeting,
since a number of people who I think would have been interested were
wrapped up with ALI-ABA.  I have asked legal counsel, in the past,
what were the problems with access, and learned:  Right to privacy
is inappropriately infringed if you give access to a donor's address,
phone number, and (if a gift is "anonymous") even just the name.If
the records give the storage location of valuable materials or of an
archaeeological site, thefts can result.  Even in museums that fall
under the Freedom of Information Act, the right to privacy applies.
     Many years ago, I interned at a museum that had two sets of files -
information files, that were accessible to all staff and to signed-in
researchers, and the registrar's files, that were confidential.  We
all do need to be careful to protect the rights of donors and
confidential sources, since where would we be without them?