Argh ... I spoke too soon.  It doesn't actually sign me out.  I looked like it.  Because it says at first that it did, whereas yesterday it just redirected me to channel9.msdn.com right away.  When I try to sign out the second time you can see that there are two services I can't sign out of:

 

Of course, I did try to clear all of my cookies and close all browser windows ... it doesn't work.