Well, in an effort to try to add to the actual topic at hand:
It's worth me noting that I've been carrying my iPhone 5 for a while now without a case. I do have a slowly peeling skin on it but that's it. I keep it in my right pocket and I always wear jeans. I have pretty good vision and I've checked my lens every time one of these threads pops up and I have yet to see any dust or anything in there.
if/when I do, it's back to Apple (well, I probably will call and have them send me a phone and send mine back but whatever)... I'm not going to waste time trying to "fix it" or telling the internet about it (unless pertinent to a thread posting asking people to share their experiences).