People too young for me to hang out with. But in all seriousness it's just a weird (and I personally think goofy) fad that came in a few years ago, almost in-line with the 10ft avi's, social ineptitude and the grunge revival. I don't know what inspired it, or why it took off besides people blindly following it and copying to 'fit in'.
I don't have anything against the people who rock it; some are really lovely. But on the whole it makes me think they're young and bad traits usually come with it. Mostly lack of basic social skills.