Amazon sues a Hong Kong-based company it accuses of paying third-party retailers to customers to write positive reviews for discounts. The company said it filed the lawsuits in a Washington state court and in Germany. Extreme Rebate facilitates payments of $2.50 per five-star review, in addition to a discount or total refund. The reviews can prompt more customers to buy the products, boosting a seller's sales rankings. Amazon banned paid reviews eight years ago, but it struggles to remove them because the activity is coordinated on external websites.