Opportunity to meet new people. Social networks like Facebook provide opportunities for you and others to meet new people, which can be a really great thing. By making new connections, you're not only being the social creature you've been designed to be, but you're also broadening your horizons and (hopefully) learning new things about yourself and the world. Meeting new people can be incredibly difficult, even if you're an extremely outgoing person, and Facebook is a great way to make connections -- and to do so with a little more background information about the person. You instantly have an opportunity to see what you have in common and to understand that person on another (albeit potentially superficial) level, making Facebook a great tool for making friends.