I like the idea, but it isn't clear to me what motivates the users to participate. Can the developer offer some sort of financial incentive to the users?
With this, they could potentially send out notifications to just their audience when participation would be useful. Completing tasks could also be a micropayment allowing the developer to give the user some sort of reward (like unlocking bonus features).
I worry that if we do micropayments for microtasks we'll end up in a very specific pigeonhole that isn't insanely interesting.