I love Facebook.
I have a huge family that is scattered all across the states (and none that live near me). And while there are some that I talk to frequently, there are many that I just don't get the chance to other than reunions or events. Facebook let's me easily keep track of everyone. What their doing for work or fun, I can see their kids growing up, etc. And I can do it at my pace and when its convenient for me. Then when we do get together or talk, we can immediately start talking about those events without the need to be "filled in" first.
And its fun to stay in touch or at least keep track of old friends that otherwise might've completely slipped away. I've managed to reconnect with good friends that I haven't seen in 15 years and been able to rekindle those friendships that I was afraid were lost forever.
Its all about how you use it and what you want out of it.