If the belt systems MEANS something then it is useful.
it is ONLY useful for the commercial school to keep students. I've known 3rd degree blackbelts who were holy terrors in the studio. but out on the street they freeze, crumble, stutter, and lose all focus when confronted in the street. i've witnessed this and was left disappointed.

i hate belt ranks, especially when for the right price my 12 year old nephew can become a black belt.