A tag-based filesystem

After working with del.icio.us and other tag-based systems, and thinking about adding tag support and other features to this blog, I started wondering if anyone had applied the "tag" concept to any other systems that are typically directory-based (as del.icio.us seems like a very good replacement for a traditional hierarchical organization (directory) of bookmarks).

Of course the first thing that came to mind was a filesystem, and sure enough, it looks like google already has a tag-based filesystem project going. That's cool. As soon as I get a little lab going here I will give that a try.