Incidentally, I've had someone (judging from the last name I get to see in the email, a Chinese person) use one of my email addresses to register a WoW account. You don't actually need to verify the email address, so they don't need access.
What's interesting is after spending 30min or so clicking around Blizzard's site there is no way to actually contact support without having an account. You also can't claim the account, because you need a first and last name along with the email address, and I only have one of their names.
In the end I just left it, it was an old account and there is no evidence that they had real access, and as it was a legacy account I'd securified it anyway (creating a massive 32character random password and storing it in a password manager, just to close off any loose ends).