Fortunately I've got a less than 2% lifetime refund/cb rate from my business; one thing I like however is Amazon's "5 refunds maximum per lifetime provision", here:
Note it says:
"Buyers are limited to a lifetime maximum of five claims for purchases from Amazon Marketplace or Merchant seller on the Amazon.com website."
And That is likely good protection from fraudulent serial-refunder type buyers, since they can only make 5 refund claims lifetime max per person.
Anyone have any experience using Amazon checkouts? Looks like it would be a super idea since it lets people use their existing amazon accounts to buy things. I'll be testing it out myself later this year. Any early adopters have feedback?