While it does appear that the tickets are showing up on the Blizzcon site, and they are allowing you to add up to 5 per cart -- we've not heard of a single purchase that has gone through as yet. It would appear that while Blizzard has done a great job of balancing the load on many of the World of Warcraft servers, the Blizzard store is not handling the zerg rush of thousands of Blizzard fans hitting it all at once very well.
So if you're hoping to land Blizzcon tickets, we suggest you grab a drink and settle in for some quality time with the fail murloc and your F5 key. We'll be right there with you.
[Update 11:13 AM EST] - Aredek on the WoW forums says that their Webfolk are looking into the problems with ordering. In the meantime, we've learned that the fail murloc enjoys mrglrgrrrlgl, long walks by the mggrgrlllrgrm, and enjoys playing gllllrmgrl when not hanging out in our web browsers.
[Update 6:03 PM EST] - While registration was open briefly this afternoon, most people have been unable to purchase tickets due to the heavy traffic on the Blizzcon site. Server fall down go boom. As of now, the site appears to be back in a maintenance phase. From what we have heard, the tickets are not sold out currently.
[Update 7:40 PM EST] The Blizzcon site is back online, however with it returns Failoc, the dreaded murloc of fail. Of course, that's when we're not seeing errors due to the server being overloaded.
[Update 12:10 AM EST] Finally managed to get an order through and confirmed. Looks like some of the WoW Insider crew have also been able to get tickets, but others are still getting Failoc'd. Good luck, everyone!
[Update 12:45 AM EST] According to Eyonix on the Blizzard forums, they are pulling down ticket ordering for the night:
We are continuing our work on bringing the website back up, however, we have decided that we do not want to make everyone wait until the early hours of the morning, hoping at a chance to purchase tickets. Thus, we will not bring up the website until after the beginning of business day tomorrow, Tuesday, August 12. We want to assure everyone that a great majority of tickets are still available for purchase.
If you've been waiting up to purchase a ticket, looks like it's time to head for bedfordshire and try again in the morning.