The Microsoft Tag application is starting to be used in the 'real world'. Last month Microsoft released the beta software, which competes with QR Codes by offering a small coloured pattern that directs users to a web page when photographed with a camera phone. This month Microsoft Tag codes have been printed in a number of US-based magazines as part of an advertising campaign for SQL Server 2008. The Microsoft Tag reader can be downloaded free from gettag.mobi and works with a number of mobile operating systems, not just Windows Mobile. Unlike the QR Code technology, Microsoft Tag doesn't store the web link but stores a reference that is retrieved from Microsoft's servers. Although this may raise privacy concerns, it also enables publishers to track response rates.[Sources: Microsoft Tag news; MSDN blogs]
For comparison, here's a QR Code: