So first, here's a Japanese blog all about QR codes:

http://www.qrcodeblog.com/

Semacodes are everywhere in Japan, from cartons of cherries to the middle of Kawasaki Station to on the cover of a magazine of job listings.

One interesting use of semacodes is on the back of menus. You can use it to make reservations over your cell phone. They even have special offers for semacode users! Semacode salad!