I emailed support and got an auto-reply that essentially said "OMG our servers fell down, went boom." Pretty much as we figured, basically. The books should be showing up as soon as O'Reilly takes care of the puddle of slag in their server room.
If this was partly a test to see how the market would respond to the $9.99 price point for tech ebooks, I'd say it was successful. Maybe a bit too successful.