Well, there was a person who spilled a cup of McDonald's coffee in their lap and got burned. They sued McDonald's because there wasn't a warning on the cup that the contents could be hot. That person won the lawsuit. Apparently the common knowledge that "Holy Crap! It's coffee that just came off a burner, I bet it's hot." didn't matter much. Now you cannot get a cup of coffee anywhere that doesn't have "CAUTION: CONTENTS MAY BE HOT" printed on it everywhere.