A methodology is needed to lock-down what files can be displayed to the user.
In particular, nautilus and the gnome file dialogs should have an optional
lockdown mechanism to restrict the user from "going around" with the GUI.
Classical example would be restricting to the users' home dirs and removable
devices such as cdrom and usbdisks (with the possibility do disable each one of
those).

Pessulus is not able to restrict it yet.

Of couse security should be applied through selinux, because if he/she can login
via command-line, the security should be enforced. But this is useful for most
of the desktop customers.