I have family and friends scattered all over the country. It easily lets me keep track of everything that is going on. Pictures of kids growing up, news (good and bad), vacations, events and parties. It allows you to keep current, while giving you the freedom to spend as much or as little time as you want on anything.
I don't see a lot of these people in person often, and I'm not one to gab on the phone or send lots of emails. Facebook has allowed me to stay closer and be at least a quasi part of more people's lives.