I'm a ebay seller with over 2500+ positive feedbacks and I'm getting quite tired of all these 'omg paypal sux!!!' claims.
First, always ship a package over $250 in value with signature confirmation - delivery confirmation is not enough to back up your claim. Second, and most important - insure the item.
All merchant account companies/credit card payment processors will initiate a 'freeze' on the charges - regardless of whether the buyer is making a fraudulent claim or not - whether it's paypal, authorize.net, 2checkout.com, wells fargo business solutions - you get the idea.
I have had this happen 3 times - because of signature confirmation I was saved on 2 items, but the third one only had delivery confirmation and I had to refund the money. However, the item was insured, and I was paid full insurance because of this claim. Now, in the event of dishonesty on the buyer's part - the insurance company can decide to investigate that person, but as far as the seller is concerned - he will get his insurance payment.
Always, always, always add signature confirmation and insurance to every shipment. If you want to go one step further you can add registered mail confirmation to it as well.