Notch posted on his twitter about a Minecraft or related ad present in the Develop Magazine, issue 119. The online version of this issue can be found here.
I extracted the image on page 43 and it is this:
http://img580.imageshack.us/img580/8995/barcode.png
I’ve been looking for a way to decode it. I have tried online decoders, downloaded SDK’s for barcode reading, I’ve had no luck. There appears to be no finder pattern within the image, leading me to believe that I am going at this all wrong and that it’s not even a Data Matrix barcode.