My take on these kind of MAs : I think this is something that would be beneficial to learn IN ADDITION TO a strong, proven, sparreable(real word?) MA base. I would probably spend a few months becoming versed in either Muay Thai, TKD, Boxing and/or BJJ, Wrestling before I went to one of these seminars or took any of these courses. . . In most fight situations you want to be able to stop your opponent but not cause permanent damage, Here in the states you will probably go to jail even if it was done in self defense. . . . But one day a situation might call for you to use deadly force against an assailant and being able to permanently damage or kill an opponent is a good skill to have even if you never have to use it.
PS: People that have no prior grappling / striking training can look at all of these videos or read 1,000 books and learn NOTHING. While the trained individual can pick up on moves and techniques just by watching the movements being executed without any explanation.