Libraries and Social Networking

What constitutes a useful web presence for public libraries? It seems to me that while certain services have become quite standard and expected-- a website for instance, an online public access catalog, and access to a librarian via email or instant messaging, there's a large gray area when it comes to other services. Is it necessary to maintain a blog? Should your library have a presence on social networking sites? Which one(s)?

I was thinking about this the other day when I was browsing my local library's website. It features links from the home page to its profiles on MySpace, Facebook, and Twitter. There's a place to sign up for the email list and a pitch for the Ask the Librarian service, with Instant Message screen names for five different chat clients. There's a link to their blog. Just a little further research turns up a web presence on del.icio.us, and three book-specific social networking sites: LibraryThing, Shelfari and Goodreads.

Truthfully, I found this to be a little overwhelming. Maybe this is reflective of my own sense of minimalism when it comes to social networking.  I'd rather concentrate on keeping one or two profiles well-designed and thoughtfully groomed than divide my attention among several sites that risk seeming redundant or poorly maintained.  

It's understandable that a library would want to cast a wide net when seeking to connect with current or potential users through social networking.  But it also seems like they might want to consider what constitutes a successful web presence.  It's possible that libraries don't think to do this sort of evaluation because there's no start-up or subscription costs with memberships to these websites.  But after all, they do pay staff to maintain these profiles, and it would be useful to know whether and how these services enhance the experiences of patrons.  What are the library's benchmarks for success?  The number of folks who friend them on MySpace?  The number of visits to a blog?  The number of virtual rum-and-cokes they're gifted on Facebook?

And how do patrons feel about the library's presence on these sites?  The place of public institutions on social networks seems fraught with all sorts of dubiousness.  Do the teenagers take your MySpace page seriously or as an awkward adult attempt at hipness?  Are you inadvertently alienating non-users of social networks by overloading the website with references to services they've never heard of, making them feel outdated and exacerbating technophobia?  Do you offer workshops to train people who might be interested to use these tools?  And are you really producing enough programming to warrant a events blog or listserv?

Tough questions, but isn't it better to have a strategy than to create something ad hoc?