Originally Posted by DarkScribe
...In the print world reviews cannot be bought in any form that would fool the public as almost every publication has its own review section...
You may be forgetting about the "blurbs," short quotes that often appear on the back or inside jacket of a book, usually penned by popular authors whom the publishers solicit directly. A single glowing sentence from a Stephen King can catapult a horror book from a lonely shelf right into a browser's basket faster than you can say "Kujo."
Those blurbs are as valuable in selling books to the public as independent reviews, mainly due to their direct association with known and popular authors and actual attachment to the product (unfortunate but true). It's incredibly transparent and obvious... but it works anyway, just as celebrity endorsements have "fooled" consumers since there have been advertisements; it is often a more powerful sales tool than independent reviews.