Guinness' novel way to present a QR code

Guinness' advertising bods came up with an interesting way of getting their product talked about: pint glasses specially printed with a QR code...

When the glass is empty, the code's unreadable:

... and even if you fill it with (for example) beer, the code still can't be read:

But if you were to fill it with a dark fluid - Hey! What about filling it with GUINNESS? - then all becomes clear:

Then, provided you're still able to hold your smartphone up to the thing without bobbing and weaving all over the place, having the phone scan the QR code apparently results in status updates on Twitter, 4square, and Facebook - as well as downloading coupons, inviting your friends to join you, and even downloading exclusive Guinness content.

Of course, if you're having a sly one (or three) during your lunch hour, the last thing you'd want is for your drink to snitch on you...

Picture source: The Dieline

Where we found out about it: Boing Boing