Only works with a dark beer like Guinness.  If, in the pub, you did scan the code, it automatically checked you into Foursquare, updated your Facebook status and tweeted on your behalf.

Wish we could get good Guinness in the USA. I’ll have to go to Ireland for some, but I would not be like the Queen and turn down a free pint; but it was too early in the morning, I would have asked for it to go.

Source: www.caples.org