The McDonald's case was legit. There was a history of them serving coffee that was excessively hot. There were a number of people who were burned before that lady. McDonalds had been told in a number of instances that their coffee was above normal serving temperatures. Their response was that their coffee is not intended to be drank when purchased, but to sit for a while before drinking.
The key here is the McDonalds knew before hand that their coffee was served at excessively hot temps, they have been notified that it was hot enought to burn people, and they made a decision to continue to serve it that way.
In the case of WDW, their cheese (at least that I have eaten) is the 'normal' serving temperature for 'hot cheese'. It did not seem excessively hot to me.
The thing with cheese is it has a large thermal mass. Hot water will quickly cool down. Hot cheese will act like a heating pad (mmmm hot cheese heating pad) and will continue to burn if not removed. If this kid got it gooped all over his face, I can see it burning.
I used to work with molten sulpher in college (it's used in testing concrete cylinders for compressive strenght). If any splashed on you, you were not supposed to try to wipe it off (because it just spread it around and make it worse). You had to stand there and let it burn (well you were supposed to stick your arm in water actualy). But it would continue to burn until it solidified on your arm. I saw one person get burned by it, and he wiped at it. His forearms were a mess for weeks afterwards.
-dave