Part of the problem with the Vine program is that there's no real need or want that other reviewers have. If I'm looking for a backup battery because it's something I need every day, and I get shipped one and it takes two weeks and then it doesn't work consistently (something that happened to me), then I'm going to have a review that says that. If I'm a Vine reviewer and a backup battery shows up and I use it a few times and it works fine, I'll probably leave a positive review and then set the item aside. The lack of need or want completely taints the review process

The other issue is that psychology studies show that being given something ingratiates a person to the giver, which also greatly taints the Vine program.