There are two reasons we don’t install Skype on the machines in Faculty Office.
1) None of the computers have mics or cameras. The mic, at least, is fairly essential for Skype.
2) We have to pay for all trans-Atlantic network traffic. Skype, by default, allows your computer to be used as a node for other people’s Skype conversations. That means that we would have to pay extra because someone in Boston or New York or Rio de Janeiro (etc.) is talking to someone in Paris or Kiev (etc.) and happen to get your computer as a ‘node’. I would really rather not do that. (http://www.ucs.cam.ac.uk/network/rules/skype.html)
We do have Skype installed and configured to not cause this sort of trouble on the various laptops the Faculty has for loan. It’s available on all of the seminar room laptops (n.b. not GR04 as of this writing) on the ground floor and on the laptops available for borrowing from the custodians. The bonus of using our laptops is that you can patch them into the network lead in your office, giving you a significantly faster speed and less latency than using wireless.