This may not impress anyone, and maybe I am just sleep-deprived and missing something, but this is what just took place. The machine I am on now has had Skype uninstalled for various reasons, but I just remembered that I have Skype (the actual application, not the executable) on my USB bar. I was able to launch it from the USB bar, and it prompted me to log in. The client opened and connected. While it lacked some functionality (for example, I couldn't see all of my account details, my contacts, or get the callto:// function to work), I was able to make SkypeOut calls, and also call and apparently initiate chats to contacts showing up in my call history window. I also called my SkypeIn number, which rang, and left myself a voicemail. I then duly got a notification of a voicemail.
UPDATE: I just repeated the exercise on a machine which has never had Skype installed, and it couldn't log me on. It's obviously looking for something which isn't there, which makes me ask, if I have uninstalled Skype from the machine where it did work, what's causing this? Maybe my uninstall was incomplete? What I'm really trying to get at is, is there a way to get a fully functioning version of Skype on a USB memory device - i.e., another angle on "pocket Skype"? And could such a version of Skype be used on a virgin PC without leaving any evidence?
UPDATE 2: I just searched the Skype forum, and whaddayaknow, someone posted this just recently.
UPDATE 3: It just gets better and better. There is a poll on the Skype forums which shows that users want such a device.
UPDATE 4: A Platinum Card value reader writes in to say that he regularly uses Skype from a USB stick on his corporate laptop due to IT policy issues. In contrast to the highly technical solution outlined in the link in Update 2 above, in his case he launches it and it 'just works'.