You know the best thing is that if you are a portal administrator but don't belong to any organization or site, you don't get the go to-menu at all. So there's no way to access control panel from the ui 
I have looked into this and in the view.jsp there's only a for-loop that loops through all sites and builds the menu. What I can remember was that it's not very easy to force the display of the control panel-link (to fix the above issue I said). Thus it might be a lot of work to remove all my sites from the menu because it's just a loop that loops through all your sites. The logic is somewhere else than in the view.jsp, might be in the alloyui taglib or deep in the service classes.
I have looked into this and in the view.jsp there's only a for-loop that loops through all sites and builds the menu. What I can remember was that it's not very easy to force the display of the control panel-link (to fix the above issue I said). Thus it might be a lot of work to remove all my sites from the menu because it's just a loop that loops through all your sites. The logic is somewhere else than in the view.jsp, might be in the alloyui taglib or deep in the service classes.