I thought it was a cool idea too. Lack of control means manipulation of rankings might be a problem to solve. You would need to ensure that spammers couldn't flood the system with fake information.
Maybe its possible to use that to the networks advantage? If manipulating the data means you need to provide additional computation power/storage... maybe its possible to find a balance?
I would be interesting to use multiple random parties to check each other. For example, have 3 independent nodes index the same site and verify that no one has tampered with the data.