What Happens When You Do “sudo rm -rf /”?
Well, now you know :)
Seriously don't try this at home. Obviously in this video sudo was used because this was a debian based (most likely ubuntu?) system; that discourages login as root. If you are using any other kind of linux system and logged in as root, you won't be even prompt for a password before everything is gone.... gone... just gone...
I always wanted to try this. Maybe I will try this on a virtual machine and post some screen shots. :)