This will allow people to mask packages based on things like RESTRICT=bindist, as they already can for PROPERTIES=interactive.
This is fixed in git: http://git.overlays.gentoo.org/gitweb/?p=proj/portage.git;a=commit;h=fcf9bec1bd756985a93bfb6843c942911eec075d
This is fixed in 2.1.11.63 and 2.2.0_alpha174.
Here are a couple of fixes for binhost support: http://git.overlays.gentoo.org/gitweb/?p=proj/portage.git;a=commit;h=7043592d0c20bcdaa3007f07e060f194a23d02ab http://git.overlays.gentoo.org/gitweb/?p=proj/portage.git;a=commit;h=5a812ae15a6c7895c71bfe78941398558c15346b