I once thought about the simple idea of a place where people could go to improve their writing for comment boxes like this one. Something like a peer to peer writer's workshop where "I am thinking about posting this, what do you think?" would be the basic question. "Here are some changes you might consider", would be the basic answer.
Monetization would have to come from the exhaust fumes...something better than adwords let us hope, but the same general mechanic of not charging for the service directly.
Anyway, mechanical turk editing is another approach. I just think its a depressing race toward the bottom of the income ladder for staff and a slimy race toward upselling for the management. Better to gamify the process.
Good luck.