This long-anticipated feature allows the world-weary PvPer to go through the list and click a thumbs down icon to the right of a highlighted Battleground. You can see what the icon looks like before it is selected on the highlighted Arathi Basin on the header image. Once the little icon is red, as you can see in the header image on Alterac Valley and Strand of the Ancients, those Battlegrounds are blacklisted. When you queue for a random Battleground, those two will be excluded from your random list.
It should be noted that the weekly Call to Arms Battleground cannot be blacklisted -- the "thumbs down" icon doesn't appear next to it. However, as you probably know, the Call to Arms changes every week, so the Battleground in question can go back onto your blacklist straight after the Call to Arms is over.
You can blacklist a maximum of two maps at a time. To un-blacklist, simply uncheck the symbol.
It's open warfare between Alliance and Horde in Mists of Pandaria, World of Warcraft's next expansion. Jump into five new levels with new talents and class mechanics, try the new monk class, and create a pandaren character to ally with either Horde or Alliance. Look for expansion basics in our Mists FAQ, or dig into our spring press event coverage for more details!