Additional details of what's going on are to be found in a "Blog" by an apparently senior Microsoft person, described by MSNBC as "David LeBlanc, a senior software development engineer for Microsoft Office."

Found via independent channels of research: David LeBlanc's Blog

Since the blog is an on-going thing, the above will only get you to the most recent posts, so something more specific will be needed to find the pertinent articles later.

How Microsoft Tracks What Is Used should go to the article immediately following LeBlanc's discussion of the blocked files. This post does contain some comments that may be of interest and applicable to the description of the file blocking.

Office 2003 SP3 and File Formats should take you directly to the blog entry on how to access the blocked files in both Office 2007 and in Office 2003 SP3.

More coming.

John