On a big billboard beside the freeway, sure. In a home for sale sign, or in a bus shelter, or anywhere else where people are either a) very interested or b) captive, they are fantastic.
Because hey, I'mma scan this QR code, and then remember about it when I'm topside.
Keep your phone hidden (but check out this QR code!)
Instead of trying to scan that QR code (in a corner of a billboard), here's the URL: http://www.btp.police.uk/pickpockets/
On a big billboard beside the freeway, sure. In a home for sale sign, or in a bus shelter, or anywhere else where people are either a) very interested or b) captive, they are fantastic.