in Unity, shouldn't the Messaging menu indicator
appear only once a messaging application is up and running? i have
neither a mail app nor an instant messaging app running at the
moment, still the envelope appears in the panel.
While it improves discoverability for the launchers in the menu,
it makes discoverability as an indicator of transient events
worse.
it also clutters the users mental model of how to launch apps
and how to use indicators in relation.
i'd suggest put Chat, Mail and Broadcast into the Unity
Launcher and add a confirmation dialog to the removal option
(Keep In Launcher).
So when somebody unticks "Keep In Launcher", she is asked to
confirm that.
The envelope makes more sense when a messaging related app is
running, imo.