That number is really surprising to me -- the vast majority of those in the queue for battlegrounds are not using the blacklist feature. Maybe it's just me, but when I queue for battlegrounds I commonly queue up with a blacklist or two (especially Arathi Basin). I wonder though if this is just a situation where people don't see it or realize it even exists. Minor changes to the UI promoting people to pick exclusions could help increase its use.
The discussion last week about blacklisting PvE dungeons brought the PvP blacklist back into the spotlight. People were talking about it, and it worked its way into a discussion with Brian Holinka over Twitter. When someone stated that battlegrounds queues are long because of the blacklist feature, Holinka responded:
Nonetheless, this is an interesting insight into how players are engaging the game.