If you were browsing a book in a store and the jacket blurb said,
“This is one of the best books of the year!”
…would you be inclined to buy it?
Before you say no, here’s something to think about.
We have a deep-seated sense of duty to authority. If we're uncertain about something we are more easily swayed by a (real or perceived) authority. We default to believing they have more authority on the object in question than we do and that influences our thinking.
Mentally, this makes the decision easy. If we're right and the book or product turns out great, then we made a good choice. If it sucks, we can default to a “bad-review” and absolve ourselves.
The idea that your next-door neighbor’s opinion may affect your decision to buy or pass up a book seems unlikely. True, word of mouth has always been a factor in the fate of successful books, but usually the mouth that the words come from belongs to someone you know, not an anonymous name on a website. But wait — when you search your Zagat guide for a restaurant recommendation, do you know who has written the review? No, but in all likelihood it’s a restaurant patron with no more professional reviewing credentials than yourself. That doesn’t stop you from saying, “Let’s go here!” Some of your neighbors thought the food was good, the place clean, the atmosphere pleasant, the service excellent, and the prices right, and that’s good enough for you.
In short, we live in an age when peer review is meaningful if not significant, and Amazon.com has used this fact to create a cadre of reviewers who must be taken seriously. Go to Amazon, click on any recently published book and page down beyond the official reviews (Publishers Weekly, New York Times, etc.). You’ll find Customer Reviews, and note that many of the reviewers identify themselves as the authors of a number of reviews. If they regularly review or blog about specific genres you may in time come to the conclusion that this person’s judgment is reliable and enlightening. Thereafter, when you see his or her name next to a review of a new book, you may very well be motivated to buy it.
Furthering the idea of authority, Amazon has created a badge system to help you identify the reviewer's credentials and review-worthiness.