Current Gnome documentation excludes addition of dbus to default run-level. It also doesn't talk about new plugdev group. Should be included.
*** Bug 145440 has been marked as a duplicate of this bug. ***
*** Bug 145439 has been marked as a duplicate of this bug. ***
dbus is not used by any gnome applications. it is in xfce and other miscellaneous apps, but it's not needed nor are there USE flags for it in any ebuilds installed by gnome. and there's no need to talk about the plugdev group; that's already mentioned in the gentoo installation handbook.