I bought a gift card from ABC Gift Cards through Gift Card Granny. I received a piece of paper in the mail with a code and instructions on how to use the gift card online or in a store.
After giving it as a gift, I got the embarrassing phone call a few weeks later saying that the store rejected the gift card because it had no balance. Luckily the person I gave the gift card to used it right away and I was able to dispute the charge. If they had tried to use it a few weeks later, I would be completely out of luck.