Most modern bittorrent client support web seeds, that is using an http-hosted file as a seed for the torrent. Ad the speed from that server to the other people who are downloading and you have much better speeds than if you were to simply download straight from the server. Add to this all the other bittorrent features, like resuming a broken download, and improved error checking and you have a very powerful downloading strategy.
Just take a look at burnbit:
http://burnbit.com/ which takes a normal hosted file on the internet and turns it into a torrent. Everyone wins!
