Illusionists and stage hypnotists like Derren Brown are well known for performing shows where they showcase their alleged expertise to make people fall into all sorts of tricks, from faith healing to Ouija board sessions.
Talking about Derren Brown specifically, I've noticed that he has been brought up on this stack in the past, in both questions and answers, but this doesn't always elicit good reactions (e.g. see this answer). Why is it so? Do renowned stage hypnotists and illusionists like Derren Brown have any scientific credibility whatsoever? Are they making use of legitimate techniques backed up by scientific evidence and research?