Library Thing is a very handy tool for those who want to keep track of books they’ve read especially since many libraries do not offer this service.

Library Thing allows people to connect with other members by joining or creating a group. They can make a group for a club, a place, a subject, or even a private group for just their friends.
Library Thing Local will connect members to local bookstores, libraries and book festivals— and to all the author readings, signings, discussions and events they host.
The statistics page contains an overview of the member and their library. It also highlights members with similar libraries, and lets them keep up with their friends' recently added books, reviews and ratings.

Facebook is a social networking website. Users can join networks organized by city, workplace, school, and region to connect and interact with other people. People can also add friends and send them messages, and update their personal profile to notify friends about themselves. The website currently has more than 100 million active users worldwide.
Facebook has met with some controversy over the past few years. It has been blocked intermittently in several countries including Syria and Iran. It has also been banned at many places of work to increase productivity. Privacy has also been an issue, and it has been compromised several times.
So, while Facebook could be a useful tool to use at RWL, the controversy would cause issues and problems that we are not likely equipt to deal with at this point.