One of the more interesting discussions I had during Ubicomp was with Tim Kindberg and a very nice chap from France Telecom who lived in Japan for a few years. He was very familiar with the state of barcode tagging as deployed in Japan, and these points stood out:
Most barcodes in use here are QRCodes and NTT phones come pre-installed with a reader. Users can also install a UPC barcode reader. The first such use of QRCodes you see is in your passport; the entry stamp has a barcode on the sticker with your id number on it.
QRcodes are so easy to read since most camera-phones in Japan are auto-focus, in contrast to our crappy fixed-focus attempts here. Our tests with QRcode reading using the KDDI cellphones were pretty successful due to that alone.
QRCode deployment in Japan is by no means ubiquitous, as reports in some blogs suggest. You find them on some products (like, oddly enough, tissue packets) but most advertising posters are distinctly QRCode-free. I certainly never saw people clicking on them in public over around 3 weeks of wandering around the country.
The telcos here draw a clear distinction between content providers and application providers. Phones aren't quite as programmable as in the West, and so most barcodes take you to a webpage portal with various actions (such as buying the product or just linking it for future reference). Of course, phones in Japan have cheap high-bandwidth connectivity, so this works very well without the long latencies and download times that we have to put up with on our carriers. We confirmed this by playing with the phones KDDI provided at the conference.
One really interesting example was that mobile phone bills sent out to people in the post have a QRCode on them, which, when clicked, is stored in one of the phone "barcode slots" in the reader application. Users then go to a post office or bank, and can pay that bill by pressing their phone against an RFID reader (which pays the bills for all the QRCodes stored on the phone). A superb example of a pick and drop interface in the wild.