So let's make it clear - no-one ever suggested they will replace normal text so there's no reason to point the fact out, as if it's a problem to be overcome - it's a bit like saying beware buying a radio, it won't replace books!
Fine Nigel, but a lot of people don't have/want/can't afford smart phones with QR readers. Bit sad to see TJJ being jumped on for making a perfectly valid point.
Personally I don't really care either way as I find sign-boards quite obstrusive right next to a site, and I don't have a smart phone anyway. But there you go.