Today Blizzard announced that they believe hackers have gotten into their system and took sensitive date. The extent of the break in is not yet completely known. They do say that they believe it is possible that personal data, including encrypted credit card information, was taken.
Blizzard has stated that the credit card information is encrypted in a way that it should be difficult to retrieve since each card would have to be decrypted individually.
In a word of caution, Blizzard is suggesting that users change their Battle.net password.
(Via GamesRadar)