Good point, Chris. You definitely have to know your audience. I don't think QR codes have gone mainstream yet, so even in developed nations it doesn't make sense to use them as a primary marketing channel. But in most places there's no harm in including them as a supplemental way to help people navigate to more information – the only cost is the time & money it takes to create them and print/post them which is relatively small.

In my city, smart phones are ubiquitous, but I only have to go 5 km and plain candy bar type phones of off brands are all I see.

My own opinion is that QR codes have their place, but since they assume a certain financial capability of a person able to have a phone to read it, you can't have it as a main marketing channel, particularly if you work in low income areas in developing nations 🙂

https://blog.ourchurch.com/2011/03/03/what-is-a-qr…

https://blog.ourchurch.com/2011/03/04/qr-codes-10-…