Quizzon, senior GM, posted this message at 8:50 PM eastern time:

The following realms will be restarted to correct some performance issues:

Azshara
Dark Iron
Malfurion
Moonrunner
Staghelm

We anticipate the realms to be back up in 30 minutes. Thank you for your patience as we address this. Senior Game Master
World of Warcraft

9:18pm (EST) - Dark Iron, Moonrunner, and Staghelm are now up.
9:25pm (EST) - Azshara back up.
9:29pm (EST) - Malfurion back up, all servers go :)

We now return you to your regularly scheduled programming.