You mention Hollywood Stock exchange, but what they're doing at Media Predict is more interesting (www.mediapredict.com).
They've gotten media companies to use a market system to actually put out content. So the crowd takes the role of editor, A&R rep, and more.
I think market-based investment systems are the way to go for crowdsourcing. Mere voting (like at Digg) isn't a good way to drive decisions -- people have no incentive to give good information.