crowdsourcing

I've noticed a recent trend of crowdsourcing amoung regular people (by which I mean non-geeks) on sites like Facebook as well as on blogs.  My wife's friends will post something like, "what's a good movie for us to watch tonight" or "I have to make supper with ground beef, what to you recommend" and they'll get a douzen responses pretty quickly.

I've been thinking about how to incorporate this into a classroom context.  Of course during regular classroom lectures I'll solicit responses from the students, but we're talking about more asynchronous interactions.  I've experimented with vocabulary wikis and forums, but students don't seem to be motivated unless there are marks associated with it.  As I see it, the motivations for responding to crowdsourcing requests are likely the desire to help, and to have your voice/opinions heard, so the challenge for us is to tap into that to get students engaged in the content.