With such attempt, even if you're unable to delete
/ entirely, you could still get your system to crash! But for that you'll need root privileges.
sudo rm -rf /
sudo rm -rf /*
will delete every files from all the RW mounts. This will case the system to crash because of possible deletion of important system files.
So it's said that you should take extreme care while working as root.
"...with great power comes great responsibility."
Protection of the filesystem root: source
In modern contex, Sun Microsystems uses
rm -rf / protection so that executing the command reports removal of
/ is not allowed. The same functionality was introduced into FreeBSD version of
rm utility. GNU
rm refuses to execute
rm -rf / if the
--preserve-root option is given, which now is the default behaviour for the command.