This annotation game was also mentioned in Bob Carpenter’s Another Linguistic Corpus Collection Game, but it merits separate mention.
From the description:
Welcome to Phrase Detectives
Lovers of literature, grammar and language, this is the place where you can work together to improve future generations of technology. By indicating relationships between words and phrases you will help to create a resource that is rich in linguistic information.
It is easy to see how this could be adapted to identification of subjects, roles and associations in texts.
And in a particular context, the interest would be in capturing usage in that context, not the wider world.
Definitely has potential as a topic map authoring interface.