With KDE SC 4.9, the kdemultimedia-kioslaves package has been removed and replaced by split ebuilds. The bangarang ebuild still depends on kdemultimedia-kioslaves.
Thanks for reporting. This is fixed in CVS now. + 03 Aug 2012; Johannes Huber <johu@gentoo.org> -bangarang-2.0.1.ebuild, + bangarang-2.1.ebuild: + Allow to build with KDE 4.9 wrt bug #429622. Thanks to Magnus Kessler + <Magnus.Kessler@gmx.net>.