QR Codes have not been successful outside of Asia up to this point, per Ad Age.
QR Codes are 2D images that are read by a reader on the user’s mobile device. The obvious advantage here is no typing for a mobile user. I believe that MSFT has a spin on this called TAG.
The downside is also obvious. There are no longer any recognizable URLs for marketers to refer to. (Not that different that what is happening with the proliferation of URL shorteners on Twitter.)
The article states that with the adoption of the iPhone and Android, QR Codes are becoming more likely here in the US. It seems that this is an excellent method for improving interactivity with marketers campaigns.