Those that know ninjutsu certainly use it. It can be used and abused. Ninjutsu is a specific branch of the martial arts originating in Japan. It is not a generic name and is not a common art. Probably the biggest abuse is the large number of places that claim to teach ninjutsu without actually having learned it. There are a number of organizations with solid links into the learnings of Ninjutsu, so do your homework carefully before selecting a school.