Given the security model inherited from 4.4BSD, it's possible to use
ZIP drives and the like without writing any setuid programs.  All the
user needs is write permission to the device, and he/she can mount it
on a directory he/she owns.  If you're at security level 1 or higher,
another user with write permission to the device won't be able to
modify the mounted file system.

Of course, there's a window between inserting the disc and mounting
it, and again between unmounting and ejecting it, where someone else
could modify the disc.  I'm open to suggestions on how to close
this...