On a system with app-admin/fam installed and not app-admin/gamin, the build of gnome-base/gnome-panel-2.16.2 fails because there is an undefined reference to `FAMNoExists'. The ebuild does not check for the dependency on gamin. Workaround: app-admin/fam must be unmerged en app-admin/gamin emerged instead. After that gnome-panel succesfully builds.
run revdep-rebuild... *** This bug has been marked as a duplicate of bug 137159 ***