QR sounds useful for some minor applications, but for anything serious placed in a public place on a physical medium (like a billboard) its a phishers dream: just put a sticker with your phishing url over the original one and noone will ever realise.
I remember temporarily sticking an A4-sized QR code linking to a mild shock image on my desk at my old job and tweeting a photo of said desk to see who I'd get a reaction from.
