It's interesting to note, too, that it's being presented during the NBA playoffs as well -- I've seen more WoW twitterers tweet about the hockey playoffs lately than the basketball equivalent. Then again, Mark also says he saw it on the NBA TV subscription service, so maybe it was targeted at people who are willing to subscribe to a digital service. And just for the heck of it, we'll also point out that it was an LA (Blizzard is in Anaheim) vs. Houston (Blizzard also has an HQ in Austin) game, so maybe it was geographically targeted as well.
But this will probably not be the last time you see WoW in this context. Keep those eyes open.