Comment 11 for bug 410254

...have just figured out how to make Empathy work via a notification area icon (there's an Empathy bug that makes it non-obvious; see #435329). However, I still think that only supporting horizontal panels isn't a good choice. Vertical panels are a completely mainstream Gnome feature and are highly desirable for, e.g., making best use of space on a widescreen monitor.

If you truly do not wish to support them, then the indicator applet should at least say so when one finds itself in a vertical panel.