Since the system is basicly a way to assign ‘experts’ on things it might be usefull to do credibility scoring per subject or maybe news-source.

I might consider reviews by stephen hawking very ‘credible’ for articles on physics but maybe less ‘credible’ for articles on cooking(as I have no idea how extended his cooking knowledge is).

This would make the system a little more complex, as you would need set terms to define subjects and it needs to be clear to the user in what context someone is reviewing an article. A article on string-theory for instance could be reviewed by a mathematician or someone in physics, which is both valid. But you might not have a physics score for the mathematician or vice versa. You do need to prevent someone with a high credibility-score on politics getting a high rating on his review on an article on math, even though he might claim the article is political.

Food for thought.