Blizzard made the following announcement today due to the downtime yesterday on the servers.

During the holiday season, World of Warcraft has experienced unprecedented popularity. We're continuing to ramp up server capacity, but in the meantime, we've seen some issues in regard to the game servers as a direct result of the extremely high traffic. Specifically, on December 22, many players were unable to access the game for approximately seven hours.

In our efforts to provide the best game experience possible, we will address this issue by automatically extending the trial period of all players who created an account on or before December 22 (11:59 PM PST) for an additional day. This will be in addition to the extension awarded previously.

We recognize that the holidays are an opportune time for gaming, and we're grateful that so many players have made World of Warcraft their game of choice this holiday season. As always, we appreciate your patience and support, and we wish you good luck in your adventures in Azeroth!