Re: But is it really a problem?
As with most things on El Reg, the people that read and comment are IT savvy and very aware of malware and scams and so won't use QR codes or the like without checking first. We are not the target for these attacks as we are likely to be a bit more careful.
Apart from just playing around in the last 10 minutes to test the Norton app mentioned above, I haven't used QR codes and I don't see that I would, but your average teenager (terrible stereotyping, I know) will see an advert showing the latest fashion items with a QR code to get more details and will be pointing their phone at it in seconds. Seeing a sticker QR code will just mean it's updated, right? It can't be anything bad, right?
The real problem is that people of that ilk will just click "OK" to any warnings or "are you sure" messages because they are just annoying and don't serve any purpose, right?
This is another case where education is what can stop the problem. Educate people that they need to check the link and that it's going to the right site, not a random site with no connection to the actual advert, and there is no issue. As with all things, the problem is carbon based, not technology based!