There's been an interesting experiment going on with a special Starbucks Gift Card called "Jonathan's Card". In short, it's a gift card which strangers were both adding and reducing the value. Think of it as a shared gift card. Simply by showing an image of the gift card's barcode (generated from Starbucks iPhone app), anyone could access the card.
Paying It Forward
I love paying it forward concepts like this and see the gift card as a natural fit. While sharing the value of a gift card is against the terms of the Starbucks Gift Card, Starbucks was actually cheering on this experiment. (It's great advertising for the product.) Looking at the twitter feed for the Jonathan's Card, there was a lot of activity of increasing and decreasing the value.
Fraudulent Use - Gift Card Terminated
Unfortunately, Jonathan's Card has been canceled by Starbucks. People can no longer add value or use it to pay for coffee. Starbuck's decided to pull the plug because some people were abusing the gift card and exploiting the nature of the program. (Not great advertising for the product.)
Apparently, Jonathan is not the only person who has clever ways to use a Starbucks Gift Card. Another developer wrote a script to check the balance of the card and transfer funds from Jonathan's Card to his own personal Starbuck's Gift Card. Apparently he transferred $625 in just 5 hours. Naturally, a person could easily sell the card to a number of third parties who sell discounted Starbucks Gift Cards and receive cash.
While this experiment is officially over, gift cards are consistently being used in new and interesting ways. This experiment also raises some interesting questions about the security of mobile apps which generate barcodes for payment; expect a post in the near future covering some of the security aspects of mobile payment applications.