Agency BBDO have created the first product activated QR Code 
and all round dynamic social media experience when having a pint of the black stuff. To get people talking about Guinness, they distributed these ‘QR Cups’ around bars. As you can see, the QR codes don’t work when empty or with ordinary beer.
When you fill the glass with Guinness however it completes the code. Scanning this QR code with your smartphone and it gives you options to tweet about your pint, check you in on 4square, update your Facebook status, download coupons and promotions, launch exclusive Guinness content and can even invite your mates along for a nice pint of Guinness.
Guinness + Social Media = lots of buzz.
Will Guinness call me a taxi after scanning my pints?
You should definitely patent that idea. I was actually more thinking of a QR code for when you reach the end of the pint it lets the barman know its time to get the next one ready