very good question. On my Reviews 90% say: good item, works well, like in description.
First: I guess that Amazon reviews have a facebook like status. I mean itīs probably nice to know that 50.000 poeple may read their comment and base their buying tendencies on this.
Second: In Germany there was a statistic that about 30% of the reviews are fake. Fake in sense of getting better prices next time or fakes written by manufacturer. This ones tend to be very grammatically correct.
I guess that this is a short time that this will be "in". The more reviews are there the less is counting the single one. Poeple get bored to write if they think it is nothing worth.
Have a look at ebay Reviews, they tend to be very, very short.
@Eguy, thatīs not what Google wants. They want to make money. Informational searches are not putting as much Money into their pokets as transactional searches.
IN the last time i see many big sites make commercials on TV again or on big sports events. I notice them since panda/penguin.