While I certainly agree with Mike that flash should cause no harm for most
materials (in fact, I've never heard that concern expressed before), I
think the two reasons that are usually given by museums for not allowing
flash photography (and the use of tripods, for that matter) are:
1. it may be (is) distracting to other visitors--probably a valid point
for art museums, but certainly less valid for history and natural history,
and
2. some sneaky image user may be able to make a good enough copy of some
valuable artifact to publish it (and thus make lots of money) without
paying the museum its normal photo and/or reproduction fee.
My view of the latter point is, I am sure, of no interest to the original
poster (it has never been of any interest to the administration of any
organization I have ever worked for), but these are the reasons I have
always heard for the photographic prohibition.  Neither should apply in a
situation like a wedding in a historic house.  Later.
David
 
 
David Haynes, Institute of Texan Cultures, PO Box 1226, San Antonio TX 78294
Voice: 210/558-2248, FAX: 210/558-2218, InterNet: [log in to unmask]