One of the benefits to Amazon owning these social networking sites for book lovers is that all of the buy links for books will go directly to Amazon, whether it be new or its used market.
Amazon continues its inexorable march to buy everything on the internet related to books. According to the Seattle Post Intelligencer, Amazon, an early investor in Shelfari, is now buying the book lover site outright. This might signal some kind of merging between Shelfari and LibraryThing.com as Amazon will soon own a stake in both. AbeBooks is a 40% shareholder in LibraryThing and Amazon is acquiring, or has acquired AbeBooks.