These torrents are extracted directly from Blizzard's downloaders. They 
transfer data with all the users downloading the file, either using 
Blizzard's downloader or using an extracted .torrent file like this. 
Check out BitTornado (http://www.bittornado.com/) if you need a 
BitTorrent client. If you're behind a router, you'll need to forward 
ports for best performance (http://bt.degreez.net/firewalled.html), 
which is one reason the Blizzard downloader usually doesn't work well. 
http://userpages.umbc.edu/~hamilton/btclientconfig.html has more info 
on actually configuring your router/firewall for BT.