MWeston said:
"Do not touch when live"
It's the feedback loop for the 5V supply and the capacitance from your body is enough to throw it out of whack and even destroy the chip. It's ridiculously sensitive but it runs fine if you leave it alone.
What would happen is a liquid got in there. Say a splash of water or a Coke? It is right next to the seam and two case openings. Or is this just a problem with the "capacitance" of our bodies and not an issue with a conductive material getting on there?
Though, I guess that wouldn't help any parts of the inside, except many things are fine once dried out, this sounds like a splash could fry the board.