It seems that keyloggers and phishers are not the only fraudsters infiltrating World of Warcraft. Halifax, a bank in the United Kingdom has ceased processing most transactions with Blizzard Entertainment. This measure was taken in response to increasing numbers of reports fraudulent transactions for WoW services. I had a similar issue with another bank based in the United States. That institution saw my recurring Blizzard charge as suspicious. Once I contacted them to verify my subscriptions my credit card was quickly returned to an active status.
In this case, the only fault on Blizzard's is making an astoundingly popular, subscription-based RPG. Do be on the lookout for unexpected transactions from Blizzard Entertainment and be sure to report them to your bank as soon as possible. Representatives from Blizzard Entertainment declined interviews with the Register, which investigated this phenomenon.
Do not be surprised if the transaction for your WoW subscription is refused in the near future.