because outbox makes sense for some use cases (social networking) but not all

I agree with will

I think of outbox as "putting stuff where it's supposed to go" which is a little tautological, but basically requires defining where any given note is supposed to go. Not defining a "correct" home for a note basically guarantees failure to find it when it's needed. Outbox as currently defined doesn't cover all cases, just (public) social media.