Efforts to implement retail 2D bar codes in stores are accelerating: Sears, in conjuction with vendor ScanBuy, became the first U.S. retailer to begin a public trial that started in mid-December at a store in Marietta, Georgia. As opposed the the traditional row of black lines (a 1D barcode), 2D barcodes look like a grid and make use of a second, vertical dimension, allowing them to store more data. What Sears hopes to do is to allow a cell phone"s digital camera "look" at a small 2D bar code on an advertisement, which launches an applet. A server interprets the bar code and the phone then launches a Web browser and deep-links to a page on that site, typically the Web site of the advertiser.
Currently, the biggest concern, which is also likely to be the most short-lived, is that the service is available on a relatively few phones in the United States. The concern about a shortage of supported phones was mentioned by a Sears manager involved in the trial.
Note: I"ve edited this to clarify that Sears is the first to use these in retail stores, since many users seem to think that this article implied that Sears was the first to use them ever, which is, of course, not true.