The current version of ether-wake in net-tools-1.60-patches-1.1.tar.bz2 is 1.05. This version lacks support for /etc/ethers. The latest version of ether-wake (1.09) adds this. I obtained etherwake_1.09.orig.tar.gz from http://mirrors.ircam.fr/pub/debian/pool/main/e/etherwake/?C=N;O=D
compiled and ran it in my gentoo environment. Seems to work as expected.
# ether-wake -v
ether-wake.c: v1.09 11/12/2003 Donald Becker, http://www.scyld.com/
# equery b `which ether-wake`
[ Searching for file(s) /usr/sbin/ether-wake in *... ]
Apparently, net-tools-1.60-r12 in the testing branch contains the updated version of ether-wake. Adding sys-apps/net-tools ~x86 to /etc/portage/package.keywords will enable the testing version.