Our U.S. online store is currently sold out of the Blizzard Authenticators, and we're working on obtaining additional stock. Please note that due to the nature of the technology in the device and the related manufacturing procedures, it will be several weeks before they're available again. We're working hard to expedite this process as much as possible.
We're also aware that non-U.S.-based players on our North American realms were unable to purchase the Blizzard Authenticator from the online store when it was available. This was due to shipping-related issues with our store for this device that could not be resolved by the time it first went on sale. Rather than delay the launch, we felt it was important to make the Authenticator available to as many people as possible as quickly as we could. We're continuing to work on a solution for these players and will provide an update as further progress is made.
The Authenticator helps safeguard account access against third-party programs, such as keyloggers, Trojans, and viruses, that are designed to steal players’ login information. This type of malicious code is often hidden in add-ons/mods and web pages and goes undetected until an account has been compromised and a thief has sold off the valuable items from the characters on that account for gold, which is then sold back to players by the third-party companies benefitting from this practice.
http://www.worldofwarcraft.com/info/basics/antigold.html
We appreciate that so many players are opting for the additional layer of security that the Authenticator provides -- playing World of Warcraft is that much more fun when you’re able to do things outside of the game, such as visit websites, with less of a worry that someone out there will be able to get access to all of your login information as a result. To learn more about how to protect yourself from people trying to steal your account name and password, please see the sticky post dedicated to this topic in our Customer Service forum.
http://forums.worldofwarcraft.com/thread.html?topicId=1778038509&sid=1