A little OT--this isn't about a warning label exactly, but about the absence of one:
Our local paper ran a story once about a bunch of good old boys who were camping out in an open field, which had a high-voltage power line running high overhead. Their tents were made of canvas with interlocking metal poles that formed the frames. After a long night of drinking, they started wondering: If they locked ALL of their poles together into one really long pole, would it be long enough to touch the power line? Turns out it was, and the guy on the other end of the really long pole got a nasty shock (I don't remember whether he survived or not.) Later on, the campers tried to sue the company that manufactured the tents because the tents DID NOT carry warning labels telling people not to lock all the poles together and touch power lines with them!