With stabilization of glibc-2.15 nss-db can not be installed anymore, because: RDEPEND=">=sys-libs/db-4 sys-apps/gawk sys-devel/make >=sys-libs/glibc-2.3 !>=sys-libs/glibc-2.15" Why its blocked? Reproducible: Always
# ChangeLog for sys-libs/nss-db # Copyright 1999-2012 Gentoo Foundation; Distributed under the GPL v2 # $Header: /var/cvsroot/gentoo-x86/sys-libs/nss-db/ChangeLog,v 1.23 2012/05/03 19:52:55 robbat2 Exp $ 03 May 2012; Robin H. Johnson <robbat2@gentoo.org> nss-db-2.2-r1.ebuild, nss-db-2.2.3_pre1-r2.ebuild, nss-db-2.2.3_pre1-r3.ebuild: New glibc now includes nss-db again, so block the new glibc here, and block nss-db in new glibc
please read the changelog