$ ls -l /dev/loop*
brw-rw---- 1 root disk 7, 0 2005-02-07 18:08 /dev/loop0
The loop is a device you don't have perms to. Your perms/owners may be slightly different, but it'd be the same idea. If you did have root.disk, you could add yourself to the 'disk' group or various other things.