I wrote about this recently, and in the past few days have noticed several posts elsewhere also exploring the issue. But you have to wonder, what incentive there will be for people to contribute their opinions, and how can contributions be authenticated and tested for accuracy?
Those most motivated to review would seem to be people with an axe to grind, either real or imagined, and competitors who try to directly or indirectly post fake negative reviews.
The Ebay feedback system has checks for authenticity and accuracy and the system is correspondingly effective; systems like tripadvisor.com don’t, and obviously suffer for it ….