Facebook, which started in 2004 by connecting people at a few elite universities to their friends at other institutions, is now open to anyone aged 13 or older with a valid e-mail address. Like MySpace, you register, create a profile and then "friend" people you know. They choose to "accept" you as a friend and your network grows. Post photos and videos, join groups, write messages and even share your blog. Privacy settings can be adjusted to disclose as much, or as little, information as you would like.