The client doesn't do anything when you log out from online.gnome.org from
the web page. From hippo-connection.c:on_cookies_maybe_changed()

     * A future enhancement might disconnect if we no longer have the auth
     * cookie, but we don't do that for now.

That would be easy to do. Some caveats:

 - If the user is logged into both mugshot.org and online.gnome.org,they'll
   never figure out that they need to log out of both. We probably need
   to use our Firefox extension to blow both sets of cookies. (Ugh!)

 - We don't get notification on cookies chnages on Windows. However, where
   IE (wininet) stores it's cookies is well know, so we should be able to
   set up a monitor there.

 - We have to make sure that the desktop-data-model is completely cleared
   back to the unauthed case, and not just to the "disconnected, information
   cached state". We may actually want to remove the cache database.
   (Though what if we aren't running the d-d-m? Then the cache database will
   still be left behind, so the advantage of blowing it in the active
   loss of auth case is maybe not so big.)