[Bridwell]

I would guess that the Pokemon grading craze accounts for a lot of these cards in the backlog. After a bunch of different Pokemon cards each sold for well over $100,000 it sent a lot of people to the PSA site making submissions. It wasn't just the Charizard cards, but lots of Pokemon are selling for some big bucks lately. Even some mass-produced commons from early sets were going for $100 on Ebay, so I think people are speculating on making some money after grading.

Some 1970's basketball seem to have escalated in price recently, as well. Cards that weren't worth the trouble 2 years ago now are worth getting graded.