It's difficult to sell an item when you have no ratings at all or very litte ratings and a competitor has hundreds, so I can understand why they give products away for ratings. I think Amazon are looking into marking those reviews more clearly.
When I am looking for something, I go by the amount of reviews, too, so I really can't blame them.
Personally, I just ignore those reviews. Reviews in the 2-4 star range are more useful anyway.
Sidenote: I refuse to buy products that have reviews like that. Instantly lost my trust.