In my experience, there is not a real use case for RDF or the other Semantic Web standards. You always have to write domain specific code to actually drive an application with RDF - so why not ditch RDF and write a domain specific data store too? How does RDF contribute, if it neither automatically drives any part of your application, or facilitates linking or relating of mulltiple datasets?

This guy expresses the problem well: http://inamidst.com/whits/2008/ditching