As Fahey pointed out yesterday, Blizzcon tickets went on sale Monday morning only to get log-jammed with a flood of errors. At 10:40 p.m. last night Blizzard decided to pull the plug on ticket sales temporarily and try to figure out what the problem was:
Update: 9:40 PM PDT - We have appreciated everyone's patience as we've worked to address issues with the BlizzCon ticket sales today. To avoid having people stay up into the early hours attempting to make ticket purchases, we will take ticket sales down and continue implementing optimisations through tonight and tomorrow morning.
There are still plenty of tickets available, so if you weren't able to purchase tickets today, please check back tomorrow. We'll continue to provide updates on the World of Warcraft forums here.
I haven't checked yet, but in theory purchasing your BlizzCon tickets today should be a much smoother experience.
BlizzCon Ticket Sales Resume Today [Blue's News]