Latest tcpdump introduces a suid USE flag in response to bug #283527. If that USE flag is set, tcpdump will be installed suid root. However, the postinst function prints an elog message unconditionally, claiming that "To let normal users run tcpdump add them into tcpdump group." I'd suggest that message to be only logged if USE=suid, as it's wrong otherwise.
Thank you Martin. Fixed in the tree.
It was fixed in 4.1.0-r1 for which I originally reported this, but it's back in tcpdump-4.1.1. Guess the bump was based on an outdated ebuild.
Fixed again. Thank you.