net-dns/avahi looks to be required by other packages that shouldn't need it (.la files pollution?)
I recently saw:
http://bugs.gentoo.org/show_bug.cgi?id=360445
dev-dotnet/gnome-sharp seems to require avahi even if it shouldn't. I
have seen that it also affects to other packages like
gnome-base/libgnome. This also sounds me a bit like:
http://bugs.gentoo.org/show_bug.cgi?id=343841