Actually torrents are pretty bad for storing "rare" files. Maybe someone should offer a fix.
I think this is mostly a consequence of how the clients work. When I download something with BitTorrent, it goes into a Downloads folder. Then I want to move and rename the files to fit into an organized collection, but then the client won't be able to find it anymore. If my client were able to track files across moves and renames, I'd be much more willing to seed things permanently. (It would also need to have good…
That's the only way this can scale for regular users, i think. And of course it may use social mechanisms like feedback "you're the reason why this rare work of art if available for everyone".
As for scalability of TCP connections , you're probably right, not my area of expertise , but once this will be declared as an important BT problem with great practical value, i'm sure some researchers would be happy to contribute and might solve this.