it is not the camera lens we are talking about here, it is the sleep/power button, you don't have to shake the phone to hear it, just walking/moving will trigger the sound, if you put your finger on it the sound stops.
The problem is that the rattling sleep button is very close to the mic so if you take video, voice memo or be on the phone hands free while on the move that rattle is recorded or transmitted. I had 2 5s's (same spec, same factory one week apart) in my hands a couple of weeks ago, one had the issue and one didn't. the apple leather case does NOT help.
My first 5s have a very loose sleep button - you could move it around in the casing without depressing it. However, an Apple Leather Case held it in place and stopped the rattle.
(Unfortunately 7.0.3 did not fix my gyroscrope problem so I sent it back. Replacement ordered.)