Mounting problems

[Bryan Scaringe <Bryan.Scaringe@computer.org>]

This is confusing the hell out of me:

I want to allow a user, AND ONLY THAT USER, to mount CD's and floppys.
We'll call him 'bob'.  I added 'bob' to the groups floppy and cdrom.
        adduser bob floppy
        adduser bob cdrom

my mount points are:
    /dev/fd0        /mnt/fd0      vfat     defaults,user,noauto   0  0
    /dev/fd1        /mnt/fd1      vfat     defaults,user,noauto   0  0
    /dev/cdrom      /mnt/cdrom    iso9660  defaults,user,noauto   0  0
    /dev/cdrw       /mnt/cdrw     iso9660  defaults,user,noauto   0  0
    /dev/mcd        /mnt/mcd      iso9660  defaults,user,noauto   0  0
    /dev/zip        /mnt/zip      vfat     defaults,user,noauto   0  0

and an ls -l of my /mnt directory shows:
        dr-xr-x---   2 root     cdrom        1024 May 18 21:51 cdrom/
        dr-xr-x---   2 root     cdrom        1024 May 18 21:51 cdrw/
        dr-xr-x---   2 root     floppy       1024 May 18 21:51 fd0/
        dr-xr-x---   2 root     floppy       1024 May 18 21:51 fd1/
        dr-xr-x---   2 root     cdrom        1024 Aug 16 21:07 mcd/
        dr-xr-x---   2 root     floppy       1024 May 18 21:51 zip/

Now, if 'bob' mounts the cdrom, /mnt/cdrom becomes:
        dr-xr-xr-w   2 root     root         1024 May 18 21:51 cdrom/

And now ANY user can see the contents of the CD!!!

Why did the group and permissions change?

How do I prevent other users from changing into that directory (/mnt/cdrom)?

Thanks,
        Bryan