Six degrees of reputation
There is an interesting article on First Monday called Six degrees of reputation. The authors mainly focused on written reviews, and not so much on the quantitative reviewing mechanisms.
They clearly put a lot of effort and thought into it, even going so far as to write an application to compare reviews to see if there were a lot of duplication (e.g. cheating).
Unfortunately it stopped at the results of their findings, and didn't actually come up with any recommendations. They document several issues in excellent detail. I would have loved to get their thoughts in the case that they were in charge of the reviews at Amazon for example.
The Reputation Guy 
on May 4, 2006 on 11:45 pm
this article also explores something i have noticed lately, using comment fields to promote websites and products. i have also seen spam promotion when a seller leaves feedback for a buyer on ebay. it has become a new form of spam that cant be deleted, ignored, or blocked.
on May 9, 2006 on 9:16 pm
I hardly ever find Amazon user reviews useful. Most are poorly written and don’t have enough information to help make descisions on purchases.
on May 12, 2006 on 1:03 am
amazon user reviews have no influence over my purchases, i only go there to buy an item, not to see other people’s opinions.