An anonymous reader writes "On December 23, Amazon advertised a 'buy one get one free' sale on DVD box-sets, but apparently did not test the promotion before going live. When anyone placed two box-sets in their cart, the website gave a double discount — so the 'grand total' shown (before order submission) was $0.00 or some very small amount. Despite terms stating that Amazon checks order prices before shipping, Amazon shipped a large number of these orders. Five days later (December 28), after orders had been received and presumably opened, Amazon emailed customers advising them to return the box-sets unopened or their credit cards would be charged an additional amount (more threads). Starting yesterday, Amazon has been (re)charging credit cards, often without authorization. On Amazon's side, they didn't advertise any double discount, and the free or nearly-free box-sets must have cost them a mint. But with Amazon continually giving unadvertised discounts that seem to be errors, is 'return the merchandise or be charged' the new way that price glitches will be handled?"