Farewell to the notification area. Canonical Design (2010-04-23):

Ubuntu is phasing out the notification area (a.k.a. "system tray"), because of its ineffectiveness at notifying people of things, and its inconsistent behavior. Many programs that previously used the notification area should use other notification mechanisms instead. Some notification area items will be replaced by various system status menus we're…

Good riddance to bad interface elements.