That'd probably work much better as long as you are able to pick a freelancer with skills or credentials matching your needs. Still wouldn't help with my Evangelion example, but would with the DNB FAQ (pick someone with Internet and psychology skills and tell them 'flag any email that looks interesting for an FAQ etc.').

On the other hand, you would also be paying even more on freelance or elance, and at that point, you're not really dealing with volunteer labor but lightweight outsourcing. (I don't know if freelancer.com even lets you pay $0 for volunteers, like Mechanical Turk does.)