I never bothered to count exact numbers, but from my experience, close to two thirds of all people, when presented with root shell and no consequences, will run rm -rf in some way.
Humble ones issue "rm -rf /usr" or "rm -rf /lib", others go straight to "/bin/rm -rf /". I've seen one person do "rm -rf /* ", immediately followed by "find / -delete". I'd really like to take a peek on his/her thought process at that moment, looked like the desire of destruction was really strong in that one particular brain ;-)
So yeah, while its not particularly useful one, there's indeed a situation where one definitely want to run it.
disclaimer: I run SELinux playbox with free root access and session recording, and peeking into what others do is also fun.
Edit: rm minus rf slash asterisk formatting.