I agree with most that reviews are generally prone to abuse. (Although frankly some of the Amazon non-serious reviews are just priceless, like the Cat in the Hat ones [1])

I am also surprised Facebook hasn't jumped in here, seems a really useful product would be 'facebook reviews' which linked reviews to profiles. Then 'the set of reviews you trust' could fall right out of your friends list.

[1] http://www.amazon.com/Cat-Hat-Dr-Seuss/product-reviews/03948...