Why CERN keeps Skype out

As I blogged a couple of weeks ago, several private (Novartis and other corportions) and public (French government research labs, universities) organizations have banned the wildly popular VoIP software Skype from their networks, for reasons that have to do with security concerns or bandwidth usage or both.
One of these organizations is CERN, the world's largest particle physics lab, based in Geneva, Switzerland. This is the place where the World Wide Web was created, so CERN banning Skype is a quite significant statement. I asked CERN's IT team for more details, and François Grey came back to me with this:

As you point out, our IT security policy concerning Skype and several other p2p software applications is documented on our website, and two pages in particular deal with this, one about Skype and one about Kazaa and others.
As you can see from this, we have no general rules, rather it is case by case and based on problems that we have observed when these applications are used on site.
In particular, I can confirm about our policy for Skype that we are concerned for three reasons:
1) it bypasses firewalls (indeed, it is designed to, and this is part of what makes it a successful p2p application)
2) it can turn user computers into "supernodes" which route other Skype traffic through CERN. Because we have good internet connectivity at CERN, this appears to happen frequently, and we have encountered some operational problems as a result.
3) we are concerned about possible legal ramifications of routing large amounts of telecom traffic through our site, as existing or future laws may require organisations that do this to store the data.
We are not opposed to Skype or internet telephony in principle, and we recognise that for a smaller institution or private use at home, the issue of supernode creation may not apply. In fact, we would be interested if a version of this type of internet telephony application became available that did not suffer from the above problems.

François also added another remark:

That said, one should be careful about using the word "free" for this type of telephony, since if an institution like CERN actually supported it, there would inevitably be some costs incurred, as is the case with supporting any sort of software. This point is often overlooked in discussions of the benefits of internet telephony.

(Thank you François). CERN doesn't just have "good internet connectivity": it has one of the broadest European pipes going through its campus, hence the issue of Skype's "supernodes" is very real for them.