It is amazing how many will instead leave outbound on 80 open. Given the knowledge at home of how to create a tunnel (not hard - just look in ssh's documentation) it is trivial to hijack that to send your X display home.
Cheers, Ben
"... I couldn't see how anyone could be educated by this self-propagating system in which people pass exams, teach others to pass exams, but nobody knows anything." --Richard Feynman