Why is Tajū Kage Bushin no Jutsu a secret?


In the first episode/chapter of Naruto, Naruto steals the scroll containing
secret jutsus and, from it, learns Tajū Kage Bushin no Jutsu, the multiple
version of the corporeal alternative to Bushin no Jutsu (which they learn in
school). While Kage Bushin no Jutsu seems to take way more chakra and is a lot
harder on the user than Bushin no Jutsu, it doesn't seem particularly
egregious. Additionally, a decent number of characters seem to use it, if the
[Wikia article](http://naruto.wikia.com/wiki/Shadow_Clone_Technique) is to be
believed. While most characters who use Kage Bushin no Jutsu don't make
multiple clones, it doesn't seem like a massive leap from one to the other. So
why is it kept secret and sealed away in the Scroll of Seals when other jutsus
that are incredibly hard on a person or even potentially fatal (like opening
the Eight Gates) aren't?




It’s a forbidden jutsu because of the amount of chakra it requires. Along with
that with certain users of the jutsu it could increase their numbers from 1 to
1000 creating a small army.

