"Our roadmap is that in Ubuntu 11.04, one year from now, there will be no notification area. And in Ubuntu Netbook Edition, well remove it even earlier, in 10.10. So if you develop an application that uses the notification area, and you want the millions of Ubuntu users to be able to use it, now is the time to change it."
So there you have it. Before even having libappindicator being blessed as an external dep for the GNOME component, they are telling application developers they can no longer depend on a standard gnome component being available in Ubuntu's version of GNOME desktop.
And to boot, they are using the estimated userbase size to strong arm developers into doing it there way..instead of using the standard GNOME upstream functionality. An estimate they REFUSE to provide a publicly stated methodology for.
Yippie for a commitment to upstream collaboration.