I've seen people do this. Nobody I actually know, though. Honestly I've always believed it's either mental illness or attention seeking. Until it can be proven otherwise I'm going to be skeptical.
I'm open to the possibility of anything though, monks can pull off some pretty amazing things (that have been scientifically proven to happen) with their bodies through meditation. I don't believe that stuff is supernatural though, just people learning to do things most other people can't.