I'm sure that's already being done, your proposal would formalize it. Sort of an amazon mechanical turk (quite apt, given the example of a chess move) but with twitter users as the 'execution units'.

The fine-grained coverage would actually be a pretty good help as well. Maybe somehow couple it with location ? First to do 'x' will get 'y', tweet filtered by something that knows roughly who is where so you don't get overloaded with things you can't do ?