You could have made the same argument 10 years ago about web and email addresses on posters. I can't say whether 40k visits is good compared to any other poster campaign, what I can say is that it's a sufficiently large number to say it can't *just* be a niche audience. I would agree that posters should include both human and machine readable codes. As for them being horrible - a) I heard that about slashes and @ signs, b) QR codes don't have to be black splodges