No one's really sure why, but Blizzard has now named the Battlegrounds groups. Check this page to find out where you've been placed-- in Bloodlust, Cyclone, Nightfall, Rampage, Reckoning, Ruin, Shadowburn, Stormstrike, Vengeance, Vindication, or Whirlwind. Note that as far as I can tell, none of the BG groups have actually changed-- all the servers are still in the same groups, there are just new names to go along with them.
And leave it to players to find something to complain about on even such a superficial change-- Ronoramin points out that three of the group names are Warlock abilities (and one is a Shammy ability-- Shaman power!), but none of them are druid abilities. A bias against droods? Tseric says no, of course, and that if they'd named them after ice cream flavors players would still be complaining, which leads to an amusing use of the phrase "Vanillacoil is overpowered!" Personally, I call Mint Chocolate Chipadins imba, but that's just me.
And as to why the names showed up in the first place, I'll guess it has something to do with the upcoming Arena PVP patch. There will be different listings and tables for each grouping, and giving them names will just make it easier to identify which Arena group belongs to which server (not to mention compare them-- I wouldn't be surprised if, maybe a patch or two after the expansion, Blizzard even sets up crossgroup Arena PVP). Meanwhile, if you don't mind, I'll start off the requisite chest thumping: VINDICATION HORDE PWNS J00, NUBZ.