A review by someone who has a direct or indirect financial interest in the product.
A review by someone perceived to have a close personal relationship with the product's owner, author, or artist.
A review by the product manufacturer, posing as an unbiased shopper.
Multiple negative reviews for the same product from one customer.
A review in exchange for monetary reward.
A review of a game in exchange for bonus in-game credits.
A negative review from a seller on a competitor's product.
A positive review from an artist on a peer's album in exchange for receiving a positive review from them.