QR codes are not uncommon these days, but you would not necessarily expect to find one on your glass of Guinness! The QR code can only be read by a Smartphone camera if the glass has been filled with the deep black coloured Guinness. So those drinkers that only like a drop of light coloured beer or lager will not be able to join in with the social media experience. So next time you see a tweet or update describing how wonderful a glass of Guinness is, you know what is going on!
This is what happens when you scan the QR code with your Smartphone;
“tweets about your pint, updates your Facebook status, checks you in via Foursquare, downloads coupons and promotions, invites your friends to join you, and even launches exclusive Guinness content.”
Source [Cool Material]