The NEWS file for dbus-glib-0.72 specifically states that the required glib version is 2.6 now, but the ebuild still deps only on >=dev-libs/glib-2.4 A quick view of /var/tmp/portage/dev-libs/dbus-glib-0.72/work/dbus-glib-0.72/configure.ac confirms that the dep is >=2.6 now.
Fixed. Thank you.