Facebook is a very noisy, very crowded place. It's irritating at points, and overbearing, and sucks up too much of your free time.
Facebook got me my current magazine gig. An editor that I knew and that knew (of) me sent me a PM out of the blue asking if I wanted to write for him.
On a more mundane level, I interact with some business contacts via FB PM. Considering most people check Facebook every day (if not every hour) and read their e-mail maybe once a week, it's sometimes a life saver. Especially if people don't answer their phones, either.
I guess it's not completely useless.
