McD's served their coffee scaldingly, undrinkably hot
I always found this one odd. In order to make coffee the water has to be between 90-95 degrees C. Obviously you can't drink it at that temperature, so you have to sit looking at it for 10 minutes or so. You would have thought that someone ordering a drink which has to be made with *very* hot water, would know that therefore the water would be *very* hot, and that they should be very careful with it.
I don't drink tea or coffee, but I have never observed anyone who has ordered the same, drinking the drink immediately. They all seem to know that it will be too hot.
It's worth saying that many of the warnings that are put on things are not because people are stupid, but because it protects the company from litigation. Hence on nuts - "this bag contains nuts".