Does mount always require root privileges?

Mounting a filesystem does not require superuser privileges under certain conditions, typically that the entry for the filesystem in /etc/fstab contains a flag that permits unprivileged users to mount it, typically user. To allow unprivileged users to mount a CIFS share (but not automount it), you would add something like the following to /etc/fstab:

//server/share /mount/point cifs noauto,user 0 0

For more information on /etc/fstab and its syntax, Wikipedia has a good article here, and man 8 mount has a good section on mounting as an unprivileged user under the heading "[t]he non-superuser mounts".

The mount(8) man page has a section dedicated to this; in short, it comes down to adding the user or users option for that mount in /etc/fstab:

The non-superuser mounts.

Normally, only the superuser can mount filesystems. However, when fstab contains the user option on a line, anybody can mount the corresponding system.

Thus, given a line

 /dev/cdrom  /cd  iso9660  ro,user,noauto,unhide

any user can mount the iso9660 filesystem found on his CDROM using the command

 mount /dev/cdrom

or

 mount /cd

For more details, see fstab(5). Only the user that mounted a filesystem can unmount it again. If any user should be able to unmount, then use users instead of user in the fstab line. The owner option is similar to the user option, with the restriction that the user must be the owner of the special file. This may be useful e.g. for /dev/fd if a login script makes the console user owner of this device. The group option is similar, with the restriction that the user must be member of the group of the special file.