Every time I read a stupid label, it will either make me laugh or sigh in disbelief because I know the label is there because someone was stupid enough to do what's being warned against (and probably sued).
For example, on a bag of generic white sugar, it read across the bottom, "Ingredients: Sugar". Gee, really? Maybe it's not a warning label, but how dumb can a person be to not know that sugar contains sugar? I've only ever seen this on that brand of sugar, too.
I've also read warnings about not using hair dryers in the bathtub or while sleeping, using curling irons externally only, and a mattress that said "Do not swallow". I would love to know who attempted that last one just so I could track them down and laugh in their faces.