@turquoise-- It probably depends on the type of disclaimer and the goal. I personally think that disclaimers work most of the time.
For example, some films where a character is shown smoking has a disclaimer that cigarette smoking is injurious to health and the actors of the film do not encourage it in any way. Now I think that's a useful disclaimer that actually works. It basically tells people that they should not take to smoking because their favorite actor is doing it on screen. When combined with images of lung cancer patients, it's a fairly effective disclaimer in my opinion.
So whether a disclaimer works or not really depend on the specific disclaimer and the reason for its use.