“”Ninja mode is supposed to be used when you are doing repetitive, remedial work like changing categories on 200 pages, cause you think "author" is better than "authors", or when you've created a new page that has 100 potential pages linking to it, adn [sic] all you will be doing is adding brackets to the word "the" 300 times. There really is no reason for it for any day to day editing.
Ninjas can make themselves bots, and thus cloak themselves from RC. Techs/mods can make people ninjas, usually after you annoy them by filling up their "precious" recent changes. The userbox at right does not appear to actually have anything to do with this group.
A list of ninjas for hire can be found here. There is no such thing as a "pirate" user group.