There seems to be an unhealthy interest and confidence in hypnosis around here. Allegedly, hypnosis bypasses a supposed instance in the mind that prevents arbitrary changes and experiences from happening.
In hypnosis, there are several huge fields; for the sake of my argument, I will focus on two of them: hypnosis for entertainment ("stage hypnosis") and hypnotherapy.
Stage hypnosis
One finds it hard to continue supporting the use of hypnosis when considering that there are several different approaches that are a lot more effective. For example, the evidence of "hypnotic" effects following the consumption of massive amounts of alcohol. Some of the "hypnotic" effects considered advanced are actually extremely commonplace when alcohol is involved. There exist countless reports of amnesia, doing things outside of conscious control, experiencing sensory distortions and hallucinations, and strong feelings of relaxation or wide ranges of unusual emotional responses.
It should be obvious that alcohol is an order of magnitude more accepted and similarly more effective than hypnosis can ever hope to be.
Even foregoing the use of alcohol as an enabling substance, it should be noted that there are completely natural alternatives to hypnosis that are considerably more pervasive in practice, such as the physiological sleep state. It is often associated with the most bizarre hallucinations (often very realistic, with a reduced ability to become aware of inconsistencies), sometimes tempered by complete amnesia, whole-body catalepsy in deep sleep states, and almost invariably a level of relaxation that is hard to match.
Another obvious facilitator of "hypnotic" effects is the presence of cameras. It is widely known that people drop into an altered state when looking at filmed material, and the same is true for being filmed: as can easily be seen by zapping through TV channels at any time of day, almost all people being filmed temporarily become completely incapable of making rational decisions.
It should be clear that hypnosis can't really be the tool of choice for entertainment.
Hypnotherapy
Hypnosis for therapeutic purposes doesn't really distinguish itself from other junk sciences. All evidence in favour of it can easily be discounted on the grounds of not being able to fulfil the requirements of empiric testability. For example, there is no known way to conduct serious double-blind experiments to test the validity of hypnosis.
It should also be noted that there is a lot more scientifically accepted evidence for cognitive-behavioural therapy (CBT). It is widely accepted amongst scientists as an effect mode of therapy. Obviously, since CBT has the most scientific support of all forms of psychotherapy, no other mode of therapy can possibly be more effective than CBT.
Another important factor in hypnotherapy is that it invariably communicates to the patient that he is not in full control of his actions and thoughts and beliefs, and doing should be considered irresponsible since a) it might get the patient to worry about his ability to function in everyday life, causing undue emotional stress, and b) arguably hypnosis sacrifices the patient's being comfortable with the mode of therapy for perceived increased effectiveness (which, as has been shown before, cannot be conclusively demonstrated).
Conclusion
There isn't really much room for debate here. Let's face it... hypnosis just can't hold up to comparison with almost any alternatives. I don't really see the point of even thinking about using hypnosis. I think it's fair to say that anyone who supports the use of hypnosis doesn't know anything. I would recommend that whenever you come across someone who advocates the use of hypnosis, completely dismiss everything that person says, has ever said, will say in the future, as well as everything that has ever been said (or will be said) in the presence of that person, his family, his friends, his neighbours or his fellow countrymen.