After doing a very quick google search on the rattle I discovered that it was a widespread issue as many of you have stated. My main thoughts were on the rattle in the lower right hand corner of the phone (the vibration mechanism) and not as much on the rattle near the camera.
I went in to the Apple store last night and showed the issues to the people there. The guy I talked to said that he had never heard of the issue before and asked if he could open my phone and check it out, so I said "go for it". He said he tightened things up and it still does it, our thoughts were that maybe the new vibration mechanism was just stronger and caused the noise (we tested with the SOS vibration holding the phone in the top left to reproduce the rattle but almost all vibrations work).
In response to this causing a long issue, as opposed to returning my device last night and just getting a new one (which may or may not have the issue), being an engineer, I opted to wait it out and see (research haha). If something does "crap out" on the device I can take it back. Further, it may aid their engineering department if one does actually "break". Also, I asked the guy, "what if I just finally get an uncomfortable feeling about the vibration (say it gets worse)?" He said, "bring it back and we can get you a new one." Sounds like a win-win to me. Just my thoughts.