Many of them are not qualified to instruct, and a lot of what they teach can get you hurt or even killed. People with military experience and espionage experience should keep to those areas. They are not experts on self-protection. I am. Moreover, there are a number of people out there who are not qualified at all to teach, and their biographies are ripe with crazy stores like, “I went to a bar in Asia and met an old guy who… blah… blah… blah…” Then, they somehow get involved with this guy and he teaches them self defense secrets that nobody else knows. Now, he can share them with you online! Woo hoo! These guys are frauds. If somebody has not been legitimately trained, and he or she does not have real world experience (not bar fights or street fights… those are fights… not self-defense situations) then you should not learn from them. If you want to learn from a professional who has been there and done that, then this is your course.