Some-one may want a copy of a web site that they have been reading but have been forced to leave the PC due, for example, to a flight. (I assume that this will not be in an air port, though. Substitute what-ever fits.) You may want to restrict it to a USB port, though (hardest to vandalize).

You would need to make sure that the operating system only recognizes mass storage devices on this port (or ports, which may be useful for users who want to copy between their drives), and probably remove write access to all but /tmp and the removable drive automount directory.

Also, changing Firefox's default download directory to a subdirectory of the flash drive (as that's the only place where users would want the data)-maybe something like downloads_from_${location}.