Aye, I'm agreeing with this one, to pay my way through uni I sold digital cameras for a living, so played with rather a lot, compact and DSLR, and every compact one without exception could have the sounds turned off. Most camera phones will have the sounds turned off if you just stick the phone on silent, any others will have an option to turn the sound off. Some DSLRs cannot have sounds turned off (without ripping the speaker out physically)
All that said, I didn't hear a single one beep during any of the talks, I must've been so totally focussed on listening to the guests that I blocked out all extraneous sound