Prediction markets have big potential. I see them coming together with micro financing/crowd funding to create a whole new sector of the economy. Bitshares X can handle some of this, but perhaps it should not become too unwieldy. I think there will be a lot more spin-offs. Bitshares Music is probably only the beginning when it comes to buying shares in content. Other content could include video, movies, books, articles, software, you name it. And then we get into events and individuals. Events: sports games, elections, award shows, etc. Individuals: Musicians, actors, athletes, inventors, artists, even college students.
To answer your question more directly, I'd love to own shares in at least half of the "crazy" ideas people have come up with so far on the forum. This will be the new economy.