I've attended Comic-con International:San Diego (formerly the San Diego Comic-Con) every year since 1989; and also attended the '87 and '80 cons. To my knowledge, this is unprecedented: The four-day memberships to the con are sold out.
I should have foreseen this when we tried to get a hotel room several months ago. Although we hit the hotel Website as soon as con-rate hotels became available, those rooms were booked immediately. We ended up with a reservation at a Holiday Inn in Mission Valley, eight miles from the convention center. That leaves the issue of traveling to the con every day, since parking around the center is almost impossible to get. Our current plan is to park near one of the hotels on the convention shuttle route and then take the shuttle in. We can pretty much write off any early-morning programs we might otherwise have attended.