Torsben,
I'm thinking that we might not want to limit ourselves to bboard messages. What if the user wants to add a certain album in the photo-album to his "favorites"? And how about that mp3 page from the mp3 jukebox module?
My thinking is that we want to make this "favorites" module (bookmark may be another good word, but there is a bookmark module already, we could extend it, but I haven't looked at it yet) available to every page of the site without having to modify all other modules.
We could do this by modifying the master default template for example, having it add a link to the bottom of the page.