I found facebook is a great web application. So far, I don't find it uses some kind of very very high-end technologies. But the way it use the technologies. It captured the way of we communicating with people in the real world and bring them into the virtual world. In the real world, that is so common we know a friend from the other friends. In the facebook, you know "friends of your friends" by the "view friends".

Today, I found a friend of my friend put the wedding events on facebook. The facebook provides the functions to check who will attend. That is so great!