udev looks for rules in 2 locations /etc/udev/rules.d/ and /lib/udev/rules.d/. system defined rules are supposed to be installed in /lib/udev/rules.d/ and not in etc, however sane-backends installs the rules into /etc/udev/rules.d/. this should be fixable by replacing the lines (in the ebuild): dodir /etc/udev/rules.d insinto /etc/udev/rules.d with: dodir /$(get_libdir)/udev/rules.d insinto /$(get_libdir)/udev/rules.d
Fix in CVS. Thanks for the hint.