When Microsoft Tag was announced at CES 2009 on January 7th, the official deadline for submitting ad material for the February 2009 issue of MSDN magazine (the print publication) was already passed. But I knew it still wasn't too late, most magazines always keep a safety buffer for late submissions. So we created a tag on the Microsoft Tag site, added the tag to our latest printed advertisement with the word "Surprise!" near it, and re-submitted February's material. It made it into the February issue! Visit the tag for a nice surprise (if you're interested in a fantastic datagrid for WPF development.)
Here is what the ad looks like (it is a two page spread ad, and the tag has been partially hidden here on purpose, you must get your hands on an MSDN magazine to get to the tag itself):

Is it the first use of Microsoft Tag in a printed magazine? Close, but there's this one, and perhaps one in a newspaper which doesn't require materials so long in advance.
Add this technology to the list of Microsoft technologies Xceed has been the first (or one of the first) to use :)