I did a small questionnaire and asked a bunch of people a few questions on what they use Facebook for; how they feel about communicating through social networks rather than having a direct conversation with someone; and if they use any other social networking sites and why they use them.
99% use Facebook to share photos and videos with their friends. And most people only have a Facebook account because all of their friends do and do not want to feel out of the loop.
Perhaps this is a change in our society today, having an online identity is almost necessary for your real life social network. It's a way to keep in touch with your old friends and communicate with your current friends as well.
Facebook stalking is also popular as you can secretly see what everyone is up to these days and stay updated with their lives without even talking to them. Sort of creepy..