That means you can populate Battle.net friends lists real quick. There's no word if Diablo III or World of Warcraft will join in the social marriage.
StarCraft II: Wings of Liberty looks to be the guinea pig for Blizz to try out integrating Facebook with Battle.net, which they have hinted at doing in the past. Likely someone somewhere will try and mod Farmville into SCII just for kicks... you've been warned.
July 27th is the retail date for Blizzard's real-time strategy franchise returning us to the universe of StarCraft. Does Facebook in your game excite or petrify you?