I always have insurance and delivery confirmation so if they claimed it didn't come my cost is covered. It definitley is all about the buyer on ebay. As a buyer I did buy a book that I never received and I filed a dispute and never got a cent, so maybe it is all about ebay. I sold an expensive horse saddle for a friend and it was the most bizarre experience I've ever had on ebay. Many many crazy e-mails, most of them demanding I stop the bidding and sell it to them at once. It was weird. I told her I would never sell any horse related items again.
As a seller I've had many buyers who simply don't pay and you report it to ebay and what happens is that they will have a dispute on their record which is the only way a seller knows if the buyer is a deadbeat. I guess you could give a negative word response even though the only choice is positive.