I'm inclined to believe this was a genuine experiment too, or at least a cool viral marketing campaign that I hope to use - for a free coffee :)

Out of curiosity, is Jonathan on HN too? It would be interesting to hear out of the horse's mouth here. I see a user with an ID of "jonathanstark":

http://news.ycombinator.com/user?id=jonathanstark

P.S. Not all Starbucks cafes accept this card/image. I tried it this morning and was told they don't accept this method of "payment."