elaborate supply chain attack eventually generates backdoored code
The email would have a link to the original .torrent and if a part of a disk was somehow corrupted, you could download just that chunk via BitTorrent instead of redownloading the whole thing or waiting for a new disk out.
Independently sourced checksums fixes most of the trust issues and a block-by-block checksum like what torrents had would allow for repair as well.
I remember installing Silkroad Online (the MMORPG) and noticing the installer used to be a clever BitTorrent client packaged with a single torrent of the game.
Server load balancing on its own.