Over the course of the last year, there has been a lot of discussion about the interaction between the real and the virtual via mobile phones, specifically about using barcodes as a unique identifier that can be read by a mobile phone's camera. In Japan and other countries, it is very common to see this sort of thing done via a type of code called a QR Code, a form of 2 dimensional barcode. There are lots of places online wh you can create your own QR Code, and many phones come with the ability to read them built in. For smartphones with applications stores, like the iPhone App Store or Android Market, there are many barcode reading apps to chose from.
Some libraries are playing around with QR Codes and other methods of annotating the real world via digital metadata. One tool that I just discovered is called StickyBits, and it takes a different model that I find really interesting. Instead of concentrating on linking physical objects to a single virtual place or information, StickyBits allows people to attach content to a given barcode, and have others see it. It's a form of tagging, but instead of tagging via terms, the user is tagging with any digital information they want: audio, video, photo, or text. For instance, a user could use StickyBits to tag a book with a video review.
Even more interesting is the fact that multiple people in multiple locations can attach multiple objects to the same barcode. It's a method of harnessing the best of the network effect, with the additional benefit of extending the tagging to any object with the same barcode. For example, it would only take one person attaching a video review to the barcode of a bestseller to make that review available to everyone who happens to pick up a copy of that bestseller anywhere. It not only distributed creation of content, but zero-lag distribution of content across real objects. This model could be used by existing library services like Librarything to attach digital objects to books pretty quickly, I would think.
In short, I think this idea has some real potential, both good and bad. On the bad, one only has to think of Chatroulette to imagine the sorts of videos that could potentially be attached to objects (if you are unfamiliar with Chatroulette, it is very NSFW...read this wikipedia article instead of visiting). But on the good, distributed enhancement of physical objects (not just books, although books are what interest me) is a powerful new way of linking the physical and the digital.