Deep semantic support is interesting for a number of places where powerful queries are needed. An example was in a project I was working on recently where the service that was used for looking up where to dispatch workload to was semantically-based. RDF/SPARQL itself is interesting because it gives you pretty rich querying right off the bat, but when you add an OWL ontology in it gets even better as it means that you can answer richer queries (i.e., that ask questions closer to what the user – and their employer – really wants) while allowing the service providers to express what they're offering more clearly too. Which isn't to say that it means everyone telling everyone everything, not at all. Instead, we had parties describing what services were provided and not what configuration they were using to provision those services. And it was all empowered by the use of semantic technologies pervasively throughout the information systems.
Currently I'm working on Taverna which is now using RDF to provide a souped-up logging system; in particular, users (especially scientists) can search through the wealth of information recorded much more easily than if they had to just grep through a huge text file. After all, it would be a little absurd if you had to use text mining to find out what really happened in your text mining workflow...
