In some countries, like Japan for example, QR codes are prolific and people user them often. Although that's not the case in the United States, and probably never will be, it does seem like there has been an uptick in QR code usage in the last few years. A new jailbreak tweak called QR Mode will certainly help its cause, among jailbreakers at least.
QR Mode is by far the best looking and best functioning QR code reader on Cydia, and it's even better than standalone app offerings found in the App Store. Its feature set is well-rounded, its implementation seriously impressive, and it doesn't feel overly intrusive. Although it suffers from a few bugs, QR Mode is well worth its $1.99 asking price, especially if these bugs can be stamped out.