On this topic, in reply to Heritage Action, the Yorkshire Dales tweeted a response:
"We have our first site panel with QR codes in production. You might like our archaeology website too http://ow.ly/42s2z"
So expect to see them more and more as time goes on...
They're completely new to me - perhaps they deserve their own thread.
I can't see any problem if they are used in conjunction with normal text - which they can't in fairness replace because not everyone owns a smart phone. Could you clarify - is a mobile phone signal needed, because if it is they wouldn't work out at Silbury.