The BlizzCon 2009 Website has the not unexpected word that yesterday's initial round of tickets for the August gaming convention is sold out, with the next batch to go on sale on May 30:

The initial allotment of tickets for BlizzCon 2009 has now been sold out. If you weren’t able to get tickets this time, you’ll have a second chance on Saturday, May 30, as another batch will go on sale then. Coverage of the gaming festival will also be offered by DIRECTV as a Pay Per View event, available both via satellite and Internet stream.