Many gamers are using BitTorrent through Valve's Steam. By which I mean, that p2p file sharing is hardly nefarious. It's just a clever use of bandwidth.
If they are not using BitTorrent then Sync would provide a new, plausible way to stop ISPs from blocking that specific protocol.
Well, apparently Blizzard does. :) Quoting http://www.wowpedia.org/Blizzard_Downloader
There's also http://debtorrent.alioth.debian.org/
Apparently CCP is planning to use bittorrent for the next generation launcher for EVE online: