x11-misc/service-discovery-applet doesn't check for the dbus python bindings properly for the modular dbus.
I commited service-discovery-applet-0.4.3 last night, it prefers dbus-python over the regular dbus package and checks for it being installed, before checking the python USE flag of the regular dbus package. I consider this already fixed, if this is wrong, be more specific with your bug reports.