I've now got the iPhone 4S and with it came to rattle.
I returned it to the Genius bar 2 weeks ago to be told it was due to the 4S having a bigger vibrate motor that spins in the opposite direction.
After spending 20 minutes explaining the noise (a very loud buzzing when it vibrates) they refused to exchange it and asked me why would I swap a new phone for a refurb one?
Anyway, I came home with my original phone and called Apple (who failed to reply to my email for two weeks) so I called them again.
The guy I spoke to was helpful this time and asked me to goto the vibrate function (settings > sounds) and turn it on and off.
I did this and he asked me to hold it closer to my home phone and told me he could hear the rattle and arranged for me to go back to the Genius Bar yesterday.
Got to the Genius bar, the guy I spoke to looked at my notes and seemed slightly surprised that the guy I spoke to actually heard it! Anyway, rather than replace the phone, he replaced the back only and brought it back out to me.
I checked it and it was still just as noisy. So I held it to his ear and made him listen to the noise.
I asked if he heard it and he said "I heard the vibrate motor" he said this twice, so I asked if that was another way of saying "no comment" at this point he smiled.
So, if the camera lenses are part of the back of the phone, then a replacement back doesn't fix it.
And I don't think the vibrate motor is at the top right of the phone because if you hold the phone with your thumb and finger at the top right and turn vibrate on and off, you can feel it, but if you do the same at the bottom right, you can feel it a lot stronger.
Anyway, they replaced my phone and the annoying loud buzzing noise has gone, but the rattle is still there.
And the last thing to point out is, when I originally spoke to Apple, I asked if he was aware of "the rattle" and he said no.
Also, Apple told me that my phone would be replaced for a new phone as every 10.000 units produced 500 are put aside for exchanges.
The Genius Bar rep gave me a phone with salvaged parts.
I think that this is a fault with the phone, and considering the cost of these 4S's I believe that Apple should admit to the fact that it isn't a characteristic of the phone, but a fault that will not be covered after your warranty has run out.
I know this as that was what I was told, even though I had brought this fault to Apples attention.
Thanks for nothing Apple.