The silent switch does nothing to silence the camera
If you buy a phone with camera function in Korea, you'll notice that taking a photo will produce a shutter sound even if you set the phone to vibrate or silent mode. This is because of a government recommendation set in 2004 to have phones always make a sound louder than 65dB when a photo is taken, to curb spy shots and boost privacy.
iPhones are no exception, and if you buy one in Korea, the silent mode switch does nothing to, uh, silence the shutter sound. This is interesting because iPhones are generally not differentiated except for slight variation in CDMA or LTE support.
(ADDENDUM: The situation seems to be the same for the iPhones bought in Japan
The question, then, would be if this shutter sound is controlled on a carrier / region basis or device basis. If it's controlled by detecting what carrier or region it's being used, then taking the phone outside Korea would silence the shutter sound. If it's preconfigured on the device, whether or not the sound will persist would depend on where you originally bought it from. So which is it?
Since I've both used an SK Telecom iPhone 4S on AT&T and am currently using an AT&T iPhone 5S on SK Telecom, I can confidently answer this question. It's on a device basis. The 4S kept making shutter sounds when it was in the United States. The 5S isn't making any shutter sounds here in Korea.
So if you're an expatriate concerned about this or just don't want to deal with shutter sounds without hassle, get an unlocked iPhone outside of Korea. It isn't illegal to use one in Korea anyway, because the deal is currently not obligated by law.