We have been using QR codes in my library for a few years. They are included in posters, placed on shelf ends (pointing to appropriate LibGuides), in the catalogue full record and in our scrolling new books display for large monitors around the library. I've captured one below.
We even have a very large QR code at the entrance (directing to our main mobile website).
Why do we use them?
QR codes are easy to make, can be small or the size of a bus, robust to deploy (the QR code in my picture still works despite being in a picture that has been re-sized and format converted) and they work really well if the end content is appropriate for mobile devices. And they are handy for public spaces where clients want use the information they can see.
Physical object --> Mobile --> Website.
If you try the QR code in the picture above you land in the appropriate version of the LibGuide.
I'm not sure that QR codes are the future of augmented reality given their lack of out-of-the-box inclusion in mobiles and low uptake in Australia. They might be a technology dead end. However they give an insight into the world of the future, where your physical surroundings will be connected with the virtual. Just don't leave your mobile phone at home!