The campaign from Northwest Airlines with 100 square meter QR Codes (the PDF below shows some photos):

Summing up the campaign, Ogilvy & Mather account executive, Yusuke Mitsumoto, says, “It is like having a new toy. People are stopping to photograph the ads. It is a treat for the tech-curious and for the poet in all of us.”

By looking at Tokyo, we can get a glimpse of what is in store for other early-adopting cities around the world. The clear trend is that almost any object, machine or advertising space can be reacted to and be a prompt to the consumer. This is the promise of the wireless digital revolution.

From Billboards That Talk to Phones (PDF)