Hmmm.
So though Box doesn't solve any shared ownership problems but that doesn't mean it isn't useful in purely heap-based circumstances. And there its feature of a little-ish fixed sized pointer to arbitrary sized data is useful. And, being a smart pointer that might point to different kinds of things, makes very interesting data structures possible.
My imagined interesting data structure might be owned by a single thread, or it might have a single big mutex policing multiple access.
I think I need to look more at what I've dismissed as "recursive data structures".
Very interesting posts here, thanks to all. I need to sleep on it, and reread this thread tomorrow.
Thanks again,
-kb