I second George Hunka's recommendation of English playwright David Edgar's playful rant against pre-show "warnings" (smoking, gun shots, etc.).
Lots of funny incidents. But also a serious point with other applications:
But behind all warnings - whether about content or sensation - lie presumptions that go beyond health and safety into more contestable areas of consumer protection. Chiefly, the assumption that seeing a film or a play is like eating a meal, in which you must have sight of the ingredients before sitting down to eat; that, above all else, the audience should be protected from surprise.
Yes, of course, draw attention to effects that might have harmful medical consequences. But retain the impetus that led an American theatre director, wearied of warnings, to post a notice promising (or threatening) that: "Something May Happen".
Personally, my favorite these days appears on before lots of TV and on DVD boxes: "This film may contain language."