Google knows that people are selfish and act in their own interests. Google also knows that good ideas don't have to be killed if they're not successful, they just need a new twist.
Google Co-op, a place "where users can contribute their knowledge and expertise to improve Google search for everyone", didn't have too much success. Google wanted to collect some meta information about web pages, so it would be able to refine results for general queries. People would find good sites and add one or more labels from a predefined set. The task is cumbersome and the motivation almost non-existent.
If people can create their own search engine, the motivation increases:
* they actually create something tangible
* the search engine might actually become successful
* people can work together for a smaller common cause with someone they trust
* there's a monetary incentive
While "search engine creators" improve their sites and add more labels and sites, Google collects this information, combines it, and uses it to label the entire web. If you think about it, the process has a lot in common with Google Image Labeler (the ESP game).
You Googled It, We Answered It
51 minutes ago