> Obviously, you can't unmount it unless your root, and root can always do
> lots of things that would cause an oops or downright crash the machine.
You want to unmount /proc on shutdown (umount -a) and it's quite important
that your machine not crash then (because otherwise your other filesystems
won't get unmounted).
In general, even root shouldn't be able to cause a kernel Oops or machine
lockup without doing something particularly evil (writing to /dev/ioport
and loading duff kernel modules are two obvious examples).
P.