After we give a presentation about the Semantic Web, we're often asked, "Okay, so what is the killer application of the Semantic Web? The "killer app" of any technology, of course, is the application that brings a user to investigate the technology and start using it. The transistor radio was a killer app of transistors, and the cell phone is a killer app of wireless technology.
So what do we answer? "The Semantic Web is the killer app."