A huge number of games used torrents for patching since around that time, notably in the MMO scene. WoW and every Nexon game come to mind. AFAIK the Battle.net launcher still downloads updates via torrent.
The Blizzard updater is actually a very cool download utility, worth hacking/poking at.
AFAIK it pioneered the concept of "web seeds", using HTTP GETs with a Range: header to download specific chunks from a CDN that were not healthy/available in the swarm.
