Jakob Lodwick writes in his essay Tagwebs, Flickr, and the Human Brain that you could create a web of tags by associating tags to other tags. This is RDF Lite in my eyes, much like what Phil Dawes is doing with TagTriples (which seems to be down at the moment). Without metatags, tags are merely keywords. And we all know how well keywords worked in HTML files. Remember ADDING, EVERY, KEYWORD, YOU, CAN, THINK, OF, TO, AN, HTML, FILE, IN, THE, META, TAG ?