Clockwork Raven uses humans to crunch your Big Data (Powered by an army of twits) by Elliot Bentley.
Twitter, the folks with the friendly API, ;-), have open sourced Clockwork Raven, a Twitter based means to upload small tasks to Mechanical Turk.
You can give users a full topic map editing/ontology creation tool (and train them in its use) or, you can ask very precise questions and crunch the output.
Not appropriate for every task but I suspect good enough for a number of them.