Or, this could lead to the birth of a decentralised web-of-trust review and recommendation system. Imagine if something like this works: When a person reads a book, he rates it according to his taste. He would also rate how much he "trusts" the opinion of any of his peers.
Unfortunately what you get with this system ends up looking like Amazon's reader reviews, because most readers are neither perceptive nor trained in analytical reading.
Viz: http://www.antipope.org/charlie/blog-static/2011/01/faint-pr...