Never underestimate financial motivation:

The Netflix Prize contest has been hailed as prime example of "prize economics" and the crowdsourcing of innovation. Prize economics refers to running a contest to generate a new innovation at less cost than an in-house research and development effort, and crowd-sourcing refers to using the proverbial wisdom of crowds to accomplish a task. Netflix has said that $1 million would be a bargain price for an improved recommendation engine, which would increase customer satisfaction and generate more movie rental business. [Link included in original post.]

The Netflix Prize -- and similar contests -- take a much-needed, practical approach to crowdsourcing by injecting clear motivation into the process. A big fat check is bound to attract a committed corps, but other rewards, such as esteem within a specific community or job opportunities, may also work (may ... successful crowdsourcing and community creation often requires a lightning-in-a-bottle moment). What I appreciate most about the Netflix Prize is that, unlike most forms of citizen journalism and community building, it clearly answered the question: "Why would anyone do this?".