There are people who believe taking photos steals small pieces of their souls. And there are museums that contend taking pictures devalues works of art that they own. There might be good reasons to restrict photo snapping. Sometimes you just want to look at something without the risk of tipping over a crouching photographer, or maybe you want to concentrate for a while without constant noise of cameras. By the way: many point-and-shoots nowadays do not really have to make all that noise but surprisingly few models let you configure a silent mode. And even if they do most people do not bother opting for annoying clicks, beeps and recorded shutter sounds.
What I find laughable is a copyright argument. They take is very seriously here. Any major attraction like a mansion that you can tour forbids you to take picture. Inside. But, they say, you can take as many as you want outside. As if they could copyright a view from the street. Or the photons that bounced of their property. Nonetheless sometimes they try to do just that: Fallingwater staff hands you a leaflet requesting that you seek their permission before publishing any photo taken on the grounds by any means including a private web album.
There were no restrictions of this nature in Mammoth Cave. But with all the crawling in narrow tunnels, drenched in water I was glad I did not have the camera along. It would probably survived, but I didn't want to risk it. So lack of photos from the cave is on me.
Not so with touring Port of Houston. They use the other excuse to disallow photography - security. Of course. Terrorists disguised as old women and small children would like nothing better then disrupt loading some container ships after taking pictures. Or blow out piles of scrap iron. Then again, there are probably people grateful the government represented by port officials is taking the precautions and making us all feel safe.
Supposedly flash can damage art. But it looks like our society does not really believe all flashes are equal. Recently Medvedev and Berlusconi asked to be photographed in front of the DaVinci's Last Supper. Normal people in order to see it have to get on 3 months waiting list. I do not really expect much from Russian leaders. At least not until Russians manage to organize fully free and democratic elections. But Italy's prime minister should know better. In modern Western democracies government is not above the law and rules. Unless of course Silvio believes that his bigger than life persona can successfully shield any damaging light from ever reaching anything that happens to be in the background.
I may agree with not using flash photography around paintings. Providing those are at least 100 years old by influential masters. Any work by lesser known artists may perish in magnesia light for all I care. This way I won't have to walk through miles of second rate paintings to see a single Picasso most backwater museums have. And they have it only because he was probably the most prolific painter of all time - depending on the source there are between 13 to 50 thousand works attributed to him. No reason to forbid photography. Flash or otherwise.