There are several things that need to happen for QR code to become an effective tool in the mobile experience. Of course people have to understand what a QR is and how to scan codes. A reliable barcode reader needs to reside on their device, and the user needs to be comfortable using the technology.
Most important—in my opinion—the scan needs to bring the user to mobile-friendly content that adds value to the experience. Merely providing a code to scan, without accounting for context or content, is a disservice to the mobile user and to the QR concept as a whole.
The campaigns presented thus far in the United States concentrate just on getting people to scan codes. Compelling, useful content seems to be secondary right now. Too many codes bring the user to sites which are virtually (or entirely!) unusable on their device.
Most content-rich, computer-centric websites are full of large images, widgets, and Flash ads. Pages like this are easy to load and render on a computer with a high-speed connection but will probably load poorly on most mobile devices. Phones typically have smaller screens, slower connections, and browsers that are incapable of handling all the bells and whistles of a full-blown website.