I think that making it too subjective will just make it gamey. You'll see different political ideologies, different religions, using it as a way to express disapproval over the perceived "bias". ... that's if they haven't already gotten there first to give the article a ten, and use it as an excuse to prevent the article from improving. "My Criticism of Barack Obama was rated a ten, so you have no right to start changing it."
I think this is a bad idea if there aren't some checks and balances.