I had the WoW thing happen as well, even though I hadn't played in years.
Gfted, they (the gold farmers) actually activate your account and then use it to do their dirty business. I'm not quite sure how they got the information, I sent a message to Blizzard about it and they said my yahoo email was compromised. I changed some stuff and everything stopped.
I wonder if it was my smartphone that caused the leak? I had bought one fairly recently, it was the only big change I had. Ah well, at least it was just an MMO account and not my bank accounts!