This is a great video all about the inappropriate use of QR codes.
There's one area where I think Scott Stratten is wrong - and that's on the issue of QR codes where there is no signal.
It's a common trope to bemoan QR codes on the tube, or on an aeroplane - but I believe it's not a very good argument.
Firstly, take a look at the posters on a typical tube train. All of them have phone numbers, SMS activities, or URLs on them - even though there's no way to use them Yet people don't laugh at them. Why? There's no way to place a phone call while on the tube, is there?
Secondly, most "underground" line have significant sections which are overground - offering plenty of opportunity to call, text, browse, or scan. And if you don't want to do it on the tube, you can always save it for later.
Which brings us on to the third point, caching. Every QR scanner I've come across has a "history" function which will let you see all the codes you've previously scanned.
So, it's perfectly possible to see a QR code on a tube train, scan it, and then open the URL when you reach civilisation. QR code scanners do not require an Internet connection to work.