From the WoW site today:
Due to some unforeseen systems issues, PayPal is not currently able to accept World of Warcraft payments. However, they are working diligently with us to bring this online as soon as possible.
We are also experiencing a brief supply delay with the retail pre-paid game cards. The game cards will be ready to ship this coming Monday, November 29 and should begin appearing in stores where World of Warcraft is sold shortly thereafter. We apologize for any inconvenience and will provide additional information as soon as it is available.
So hang in there people. You'll be able to join the rest of us very soon!