UPDATE: Saturday has now sold out, Friday is almost gone. The site is now telling recent signees that they do not have a chance of getting a ticket now…
That was fast. At around the half hour mark of going on sale, the four day ticket for San Diego Comic Con 2012 had sold out. There are still single tickets but if you're still in the queue (as I am), it will be single day tickets only.
The show had stopped doing reduced prices on the four day ticket, so as to stop people going for three days buying it anyway. This doesn't seem to have reduced its appeal however.
It is also possible some people will return their four day ticket, as they are no longer able to attend the show, in which case San Diego Comic Con will release those at a later date.