Only five of you do not use Facebook regularly. Facebook claims to have over 250 million users.
The authors, Sodt & Summey, cite the 2007 Pew Report that over 50% of teens have social networking profiles, but more recent Pew studies suggest that number is now over 60%. Pew Internet & American Life Project's December 2008 tracking survey found that 35% of adult internet users have social networking profiles, up from 8% just four years ago(1). Whichever numbers you look at, it is clear that social networking is booming.

Sodt & Summey mention MySpace, but they fail to point out the significant problems with MySpace. Their example is the Brooklyn College Library. As is so characteristic of MySpace, the comments board is littered with advertisements. Facebook offers libraries more benefits and as the authors mention, Facebook continues to evolve.

How can libraries make use of Facebook's potential?
Libraries once started Facebook Groups when that was a new development, but those have mostly been abandoned. Facebook groups are often static entities that a user joins in order to define him- or herself, not to participate or interact with others.
Facebook Pages are the prevalent choice now after being introduced in November of 2007. They are designed much like an individual's profile and can feature apps. The most common app is a catalog search, but some other handy ones exist, like WorldCat, LibGuides and Books iRead.

Public Libraries on Facebook:

Seattle Public Library
Manchester Library & Information Services
Bangor Public Library

Law Libraries on Facebook:

Sacramento County Public Law Library
Georgetown Law Library

Academic Libraries on Facebook:

Georgetown Law Library
University of Philippines Dillman University Library

Medical Libraries on Facebook:

Florida International University Medical Library


Ageism

The authors point out that Facebook can be used to reach the millennial generation- but in fact college students are no longer the fastest growing demographic on facebook: 35-54 year olds have taken an impressive lead and sideswiped the echo boomers.
iStrategyLabs reports that in the last six months, five million people between the ages of 35 and 54 joined Facebook. Admittedly, the percentage of young people on social networking sites is much, much higher than the percentage of older adults (1).


Netiquette

Sodt and Summey suggest that "librarians can use their personal profiles... to answer questions, post items to talk about favorite books, albums to share pictures of library events, and events to share scheduled events like workshops or library classes." While that is a lovely idea, what about those of us who have pre-existing Facebook pages? As with educators and other professionals, librarians should probably separate personal web space from their work life.
Younger librarians, who already have personal profiles, might need two separate Facebook profiles to maintain a division of professional and personal affairs(2). This is particularly true with private libraries where an image of professionalism is very important. If a librarian works at a law firm, it might be best not to friend that law firm's library facebook page if his or her personal facebook account is anything other than a business profile (3). The solution for many librarians may be to use LinkedIn for professional profiles and Facebook for private profiles.
Some libraries have decided to create policies for this murky area (4). The Monterey Public Library has a very good example of a social networking policy.

Facebook Groups for Librarians

Facebook Apps for Libraries
Librarians and Facebook
Library 2.0 Interest Group

References:

(1) Lenhart, Amanda. "Adults and Social Network Websites." Pew Internet and American Life Project (January 2009).
(2) Sekyere, Kwabena. "Too much Hullabaloo about Facebook in Libraries! Is it really helping libraries?" Nebraska Library Association Quarterly v. 40 no. 2 (Summer 2009) p. 25-7.
(3) Lapachet, Jaye A. H.; Rubin, Andrea. "What's on the Library's Mind? Facebooks's place in the law library." AALL Spectrum v. 13 no. 9 (July 2009) p. 20-1, 28.
(4) Kroski, Ellyssa. "Should Your Library Have a Social Media Policy?" School Library Journal (October 2009).
http://www.schoollibraryjournal.com/article/CA6699104.html

Further reading:

Pasek, Josh; More, Eian; Hargittai, Eszter. "Facebook and academic performance: Reconciling a media sensation with data." First Monday (Online) v. 14 no. 5 (May 4 2009).
http://jcmc.indiana.edu/vol13/issue1/boyd.ellison.html
(via Library Literature & Information Sciences Full Text database)

Friends: SNS for Engaged Library Services : Friends: Social Networking Sites for Engaged Library Services is devoted to the use of online social networking sites for any and all types of library-related programs or services.