In day-to-day usage, Skype isn’t much of a bandwidth hog; the real trouble comes when your computer makes itself available as a “supernode,” allowing Skype to route other calls over your connection. This can place a huge demand on your network connection, increasing by in some cases up to a gigabyte a month. Supernode mode can be disabled, but Skype doesn’t provide a method for doing it via the program itself.
The ban does not affect dorms and residences, and reps from Skype parent eBay are en route to discuss with the university ways to handle the problem without banning the program entirely.