The McDonald's case regarding the coffee was an excellent example of media sensationalism. The issue was not "the cup did not warn it was hot", this was rather a comedy bit on the case that played well in the media. The issue was the coffee was overboiled and was 20 degrees (C not F) above the temperature it was supposed to be. Thus the person suffered much more severe burns when they spilled their coffee. And they sued for their medical costs. As this wasn't a lawsuit against a doctor it doesn't even effect the cost of malpractice insurance.

The precise ruling was because the coffee was far beyond the expected normal temperature that a reasonable person would expect coffee to be, yet carried no additional warning (either spoken from the attendant, or written on the cup).

Btw, when they serve me cold coffee and I sue them for false advertising (the cup said Caution: Hot!) is that a frivolous lawsuit?