Now since Canonical is obsessed with the "libappindicator" type application indicators which is the single most important idea that defines their new "Unity" desktop... they are trying to convert these Gnome panel applets to indicators.
But if they do so and completely remove the applets from Unity, then those programs that rely on Gnome applets won't simply run!. According to an Ubuntu developer, Martin, there has been a long discussion concerning the issue as well.
So they could make the decision to simply ignore the applets and convert them into "indicator icons" thus resulting few of the major applications not to run in Unity OR to create a white-list of apps and only to keep those applets needed by those applications in Unity. So when they release the long awaited Unity desktop within the next few days and some of the popular applications fail to work due to "missing Gnome applet" support, then I think you can guess what happened!.
Anyway, according to Martin, there are few proprietary applications that need these Gnome applets and it would be interesting what percentage of GNU licensed vs Proprietary will be white listed. And let's hope that Canonical would not disappoint their loyal users by simply not letting few popular apps not to work in Unity because of this "conversion" thing.