Maybe the iBook is made of pure, white cocaine?
It's probably just a run-up scam, but it might also be poor eBay strategy. I found that when bidding on items that I'd really want (mostly books) I would see people who, no matter what bid I entered, would always outbid me by the bid amount ($1, $5, $.25, whatever) as soon as I sent in a bid. The more I entered bids, the same user would keep outbidding me the second I entered them.
After a while (usually when the item in question approached actual retail value, or the value I could find at a bricks-and-morter bookstore), I simply gave up bidding. When I checked back at the items after bidding ended, the same user would have won the item, usually after outbidding others in increment-after-increment bidding.
I guess where this is all going is that the winner might have put in an outrageous bid amount and banked on the premise that no-one else would bid on the iBook after a certain point because it would be less of a deal. Maybe the previous bidder did the same, and together the two entered $12,000 and $12,100 as their maximum bids. After the second party entered an amount over the outrageous bid from the first person, eBay took over and ran the iBook right to the end of the highest bid.
After all this writing, I'm still leaning towards a run-up scam (especially if you look at the bid history and that the winner is no longer a registered user) - because only a true idiot would bid $12,000 at once to win an iBook. But, I have seen folks do what I described above, and it seems to work for them.
Now if I were the seller of said iBook, I'd be having a party right now (or not, since it's unlikely I'd get my money).
