> Since filming, editing, and streaming videos already consumes users' storage and bandwidth resources anyway, the total amount of resources available to a P2P torrent-style network clearly is already in the ballpark of what's needed for YouTube.

I doubt it because a lot of this content doesn't exist outside of Youtube and because the content does exist on external drives has not internet connectivity or capacity to get it.

> No idea how well it works in practice, but in theory PeerTube has already solved this using WebTorrent.

It seems to currently have 220K users, not exactly what I would call representative or a success for that matter.

> The nice thing about P2P is that your network's capacity scales organically with load. More users⇒More capacity.

Only if they agree to themselves share the content they host which is not necessarily the case.