It's not just my skin, I've seen other things smudge the paint. It's usually when it gets pretty hot or sunny out. Keep in mind different products use different kinds of paints. Humidity and temperature can effect the paint as well.
I seriously doubt a "bad diet" is what's causing this. I eat pretty healthy anyway: vegetarian and mostly home-cooked meals from scratch. But I find it a bit unscientific, as well as more than a little demeaning, to jump to the conclusion of life-style choices being the culprit for a product's failure.
I meant no offense Eric.
I'm just speaking from the experience of my guitar repair business, and how I see corroded hardware from kids who eat nothing but Taco Bell, and they wonder why they have bad acne and why their hardware plating is acidizing & such. My comment wasn't meant as an attack on you, as I have had no insight into your health habits until you just provided clarification. I was just making a generalized offering of information for an added perspective.
You are correct, one's geographical environment can indeed influence the issue, as well as quality, or lack of, the original paint job.
I live in the Seattle area, where we get very consistent rain except for about 8 weeks each year. Personally, I've had my Laboratory 49 since March/2012 and it's always in the same room with climate control, and I have not personally had any issues with mine. Perhaps mine is the exception.