I ran across a 2 year old piece from VoIP News out of Australia that suggests some industries want to ban Skype. Given the various attempts I've heard about with regards to blocking Skype, I can't say I'm surprised, but I don't think it's going to happen.

Skype runs on many different platforms: Mac, Linux, Windows, mobile phones, and hardware phones. To call a moratorium on Skype and have it be enforceable is next to impossible. Then, of course, there are other attempts to block it. Skype encrypts all traffic so it looks like an opaque blob. That's what good encryption is supposed to do!

Certainly, there are some regulatory requirements that Skype doesn't meet, and in those regulated environments, Skype might not be the most appropriate things to use. Technical solutions aren't the answer here, getting the end users trained on proper behavior is.