What needs x11-libs/libxkbui?
> equery depends doesn't show anything ... so I followed emerge --depclean's
> suggestion and unmerged it. *Have I borked anything?
Most probably not.
I generally trust --depclean, But I generally follow --depclean's
advice and run revdep-rebuild afterwards.
> I'm asking this, because it also suggested I remove dev-libs/boost-1.41.0-r3
> and dev-util/boost-build-1.41.0, but akonadi would not start without them
> (dbus error).
IMO, if akonadi depends on boost, the ebuild should reflect that. Have
you tried rebuilding akonadi?
(Did you ran revdep-rebuild?)