Now that I think about it some more, this is a problem that WinFS could really help to solve.  The biggest reason that people don't use things like RDF is sheer laziness (you'll notice the rich RDF on my site ) but if we can use the Longhorn interface to easily enter and organize metadata about content, it might be a cool way to generate RDF or other semantic information.  Hmmmm...  It would be fun to write a WinFS -> RDF widget.  If it wasn't for that dang day job...