Looks like gvfs-1.14.2 can be successfully builded at least with >=net-fs/samba-4[client]
Btw gvfs-1.16.0 is out (it compiles/works with samba4 too)
So, maybe, "samba? ( >=net-fs/samba-3.4.6[smbclient] )" rule should be extended (samba4 doesn't have use flag smbclient)
1.16 is part of gnome 3.8 release and is handled in another bug report.
*** This bug has been marked as a duplicate of bug 452050 ***