Formats: Codes from mobile devices should point at resources formatted for mobile devices. Audio works well on phones (duuh!). Video may or may not do - the QR codes on Pepsi cans point to a video which doesn't play on iPhones - what were they thinking? Do students want to pay to download a one hour video of your lecture - I think not. Do we devote enough resources to generating mobile-compatible materials, and if not, will the rise of QR codes force us to do so? And what does it all mean for accessibility?
Security concerns: Could someone edit a physical QR code to produce an undesirable result? Are QR codes trusted resources - where do they lead you? Phishing? Viruses?
Much thinking still to do.
Here are Andy's thoughts on the meeting, including these nice mindmaps.