Well, I just did a test here, with the NX2000 - slapping the poor camera against my chest many times and never did it trigger anything. I'm quite sure a modern capacitive touch screen is quite good at determining what is a finger and what isn't.
I have the same issue with the NX300, it does not do a great job determining that. I think it might have to do with temperature or humidity. Maybe a little sweat on the shirt from being out in 90 degree weather. When I would take my NX300 to the zoo I would probably have 5 or so shots from the camera swinging around and brushing up against me and triggering, and the focus point in random spots.
Even with my NX30 I noticed the same. At a wedding this past weekend I noticed there were probably 3 or 4 shots of nothing. Outdoor wedding and it was 30°C (86°F) and humid. I also noticed the focus point was wrong several times (usually in the far corner where it is hard to spot).
Eric