Making Connections and digital cameras

Several people here at Making Connections are taking photographs of slides in presentations using their digital cameras. Don't mind that at all. But there's a certain irony in the fact that these cameras make artificial noises - beep, beep, clickety click, beep, beep, clickety click, beep, beep, clickety click, which disturbs people around them. This to me comes under the heading of politeness as I have blogged elsewhere - do please take photos, but do please switch the sound off. It's your toy, you ought to know how to use it. I twittered this and was told by somebody else that they thought the sound could not in fact be switched off on some cameras, and in fact it was illegal, they thought, in some jurisdictions to take photos silently because of privacy issues. I'd like to know if that's true, but if that is the case then the owners of those cameras should not be using them in a situation where they disturb other people.