There was some sort of hassle over this several years ago. In South-Korea they actually passed a law in 2004 mandating the use of 64-decibel "shutter sound". In Japan the manufacturers just pre-empted the law by common agreement. I'm not sure if the law was ever passed there but you just can't get a device (regardless OS) without shutter-sound there. You can't even turn an iPhone sold there into silent-mode to disable the shutter sound.