Arthur from the Computing Service recently blogged about how the University's connection to the outside world gets used:
Here black is the overall, purple is streaming protocols and green is “standard” protocols (including http, email etc). A lot of people are watching a lot of videos and/or playing flash games.
(BTW If you’re wondering how academics ever get to do any work, most of that video is actually going to the student study bedroom network rather than the main campus network)
Some quick stats on the Uni’s external link