Here's an article from a literary agency director considering which social networking platform is better for writers, Facebook or Twitter.
I find that between my FB and Twitter pages, more writers -- and readers -- actively share on Twitter than on Facebook. I agree with some of the commenters who've said that Twitter is a great way to meet writers and introduce their work. FB is a good place to build on the relationships begun on Twitter.
What do you think?
BookEnds, LLC — A Literary Agency: Social Networking: Twitter v. Facebook: "As you know, I’ve been thinking a lot about social networking and how authors can best use it for promotion, and one of the things I have been dwelling on is Twitter v. Facebook and which is really the more powerful when it comes to building a readership because, let’s be honest, that’s our ultimate goal."