"I just thought I would also say, I am part of the Vine program. So I got the item free. If I don't give enough good reviews, Amazon will stop sending me all this expensive free stuff. But don't worry, it hasn't affected by reviews, at all."
That's not what happens on Vine, is it? The vendor doesn't know who gets the kit. They just make x number available for review, and Amazon allocate them. AFAIK, the reviewer isn't bullied to give a 5* review since they are not out of pocket if their give a poor review. Specifically, Amazon hands the stuff out for free.
I'm not especially knowledgeable about the Vine programme, I did exaggerate (but in a way, which tended to highlight the reality of the situation, as I see it) the situation and I can believe that technically speaking, you are right about it.
But in practice, my opinion is that I've NOT seen any icon or anything (in general), identifying people in the Vine programme. So it is not that noticeable (at least to me), except sometimes where it says top 500 reviewer or something and/or there was a disclaimer somewhere in the product review (usually towards the end of it), which says it was a Vine and/or given free product review.
My opinion is generally against it, because they are apparently using psychological and/or statistical techniques, to manipulate the reviews and hence the sales of some products.
Reviews should be unbiased, real/genuine things. Not things created/manipulated by the sellers and/or Amazon.
Because of my opinion on this matter, if/when I see the fact that there is at least one Vine review. I'm immediately put off buying the item, and become rather suspicious of it. If the item is such a bargain and/or good value for money and/or liked by so many people. Then why hasn't the reviews been allowed to build up, naturally.
But, on the other hand. I do see/understand that brand new products, have initial slowness/difficulties. Because of how long it needs to (unassisted), gradually build up sales and reviews. The programme does seem to aim for that very situation, so that does tend to sway my opinion into somewhat agreeing with the concept.
They should make it much clearer, when they are semi-professional/free-product reviews. Maybe by making the text a different background text colour and things. I (in particular), can't easily tell they are Vine reviews.
EDIT tl;dr
What I think Amazon should have done, is as follows.
Made/enforced that all user reviews, are genuine/honest affairs.
Created the concept of official (or semi-official), AMAZON (extra) reviews. I.e. Amazon endorsed/created/written reviews. Then that would be honest and fine.
I.e. it would look something like this:
Selection Boxes::::[User Reviews] [Amazon Vine Programme Reviews] [External/Sellers Extra Reviews]
Then the users of Amazon can choose, what types of reviews they can see, and make their mind up, in a fair way.