I've hit no available tickets 4 times now. My advice to everyone reading this is to keep trying until 8AM in case they are releasing the tickets in batches.
EDIT: Definitely batches, got 1 at exactly 7:15.
It's pretty clear that Google needs to restructure this event if they want it to continue to have meaning as a developer conference. This sort of waste of people's time, only to have tickets sell out in 30 seconds or whatever ridiculous number is just not valuable.
What would Google have to do to maintain the substance of the conference? Simply promise that there won't be any free toys given away? I missed out on I/O 2011 after having attended in 2009 and 2010 because bad people went simply for the hundreds of dollars worth of free and early-release hardware Google hands out.
I would have paid 300 dollars for the conference regardless of whether Google gave me the latest gadget.
We were using Google Checkout to do registration for the Singularity Summit and ran into this problem, and the answer is basically yes.
That said, I don't have one. Waiting for an academic ticket too.
Edit: I got "no tickets available at this time" several times before getting through so don't give up.
Edit: All tickets sold out. There goes my plans to visit the US!