Actually Kenzan, it may be you that is surprised. While I don't practice any of those arts, there are three separate large organizations, all based in Japan, that teach ninjutsu as a part of their curriculum. They are the Bujinkan, the Jinenkan, and the Genbukan. They are all somewhat related to each other, and teach from the same root systems. In addition, some of the koryu still teach ninjutsu as a part of their sogo bujutsu. Ninjutsu simply refers to "stealth techniques" or "spy techniques". It is the association with many wierdos on both sides of the Pacific that have given anything "ninja" a bad name. That about exhausts my knowledge of the subject.