Somewhere, either here or in the Amazon Kindle Users forum I
think I read a post saying that Amazon Gift Cards couldn't be used to purchase downloadable items. I asked Kindle Support about this yesterday and received this answer tonight.
Hello from Amazon.com.
Using an Amazon Gift Card to buy content from the Kindle store is easy. Simply redeem the Gift Card to your Amazon.com account before you make a purchase. When you click the "Buy with 1-Click" button, any available Gift Card balance on your account will automatically be applied to the purchase before your credit or debit card is charged.
Content from the Amazon Kindle store is only available to customers with a credit or debit card issued by a U.S bank with a U.S. billing address listed as the default 1-Click payment method. To successfully complete your purchase, you must have a valid payment method listed even if you intend to pay for your entire purchase with a Gift Card.
Note: Amazon Gift Cards cannot be used to pay subscription fees.
Information on this topic also appears on the Kindle Support pages at this URL:
http://www.amazon.com/kindlesupport
That's a relief since I hope to get Amazon Gift Cards this Christmas and will use them to feed our growing ebook addiction! I may even have my very own Kindle by then.