Question: What are people actually doing with technology like this right now? (i.e. who are the people who see this and think.. yay, I'll sign up now!)
Obvious uses would be any kind of CMS. Investigative journalism is another.
I've recently started exploring the Legal Informatics field. The problems in it are huge and typically involving adding some structure to lots and lots of unstructured text.
Also, Peter, if you do end up reading this, great work on the stuff you do :) Big fan here!