Own goal for Amazon
one of Amazons selling points (for me) is the fact that a lot of things they sell have a body of genuine reviews behind them. It's not scientific, but looking at my looked at list and purchases, I'd wager that I've bought more because of good reviews than not bought because of bad reviews.
(Bearing in mind that sometimes it's not a "bad" review, just one which highlights a products particular suitability for a specific job. I may still buy *another* product from Amazon.)
If the words starts getting out that Amazon reviews are (or can be) stacked, then they will lose one of their key selling points for me - and my wife.
Be curious to see how Amazon proceed here. Up until now, they have hardly put a foot wrong (in my opinion) since 1997 when I started using them.