I mean, if we continue with that logic you're actually providing it to your ISP, who does what they think will profit the most. That is, delivering it to Amazon. Who will then deliver it to others looking to buy that product.

Is it so far fetched to think amazon might manipulate reviews? Yelp and Glassdoor do.

I'm sure they do, at least to some degree.

Sort of beside the point though - I don't actually care about the impact, good or bad, on Amazon. If I write a review it is to help a fellow consumer. If I think my review instead hurts the fellow, or has no effect, I won't do it. But how it impacts Amazon simply doesn't matter to me.