In a modern GUI (lets take Windows), you should be able to right click on any window and be able to grab some rdf from any app (like an mp3 player and the rdf would be what song it is playing)and be able to paste that rdf into another app. What that "other app" does is independent of where you got the RDF - though of course, presumably some of that RDF that is recognized by the receiving application. Unrecognized RDF assertions would just be ignored.
And then maybe even the apps can let you configure how to map application-specific state into RDF (and back to application-specific state or functionality).
I guess there's some facility for this in windows cut-n-paste for limited data types (URLs for example), but if it were just a standard data format, then it would be something that multiple applications could loosely coordinate around, esp. as more useful RDF ontologies and vocabularies are evolved.
