It has been widely reported that Amazon scrubs the negative reviews on their site. We don't have to assume anything to understand that Amazon doesn't value transparency - Amazon has not released any information (that I've seen) explaining their stance on removing negative reviews. But why would Amazon remove negative reviews?
If you were working at Amazon, why might you scrub reviews? I would bet two shiny nickels one might remove negative reviews to sell more books. I've bought or not bought at least one book based on the reviews. I'm sure Amazon has statistics on how consumers shop, and has quantified my anecdotal evidence. It wouldn't surprise me if highly rated books, regardless of content and some control factors, sell more total books for Amazon.
Now ask yourself, what is the downside of choosing to keep negative reviews floating around? The most obvious factor is Amazon's long-term credibility with the consumer. Leaving their reviews off the books would leave your consumers miffed; you are ignoring their opinions and they would trust the reviews they see less.
If we assume (explicit note of assumption) that:
* Amazon sells more books short-term by leaving negative reviews off the web-site
* Customers will become angry long-term if Amazon is deceiving them
then we have insight into Amazon as a corporation. Amazon, under these set of assumptions, values short-term profit more than their consumer's long-term concerns. It seems that one could draw a host of other conclusions about Amazon and their principles and values, but this would be a bit complex and there is lasagna in the fridge.