Amazon Vine™ Program というものがある

What is Amazon Vine™?

Amazon Vine™ is a program that enables a select group of Amazon customers to post opinions about new and pre-release items to help their fellow customers make educated purchase decisions.
Customers are invited to become Amazon Vine™ Voices based on the trust they have earned in the Amazon community for writing accurate and insightful reviews.
Amazon provides Amazon Vine™ members with free copies of products that have been submitted to the program by vendors.
Amazon does not influence the opinions of Amazon Vine™ members, nor do we modify or edit their reviews.

Amazon.com – Amazon Vine™ Program