From blog post: "Concretely: can I write my own client to present a filtered view of the Corporation X data stream, or have other people do that for me?"

The answer is yes but most of users don't use it like that. it is what it says it is, database of people. and a way of reaching them. Before this you couldn't acces most of them but only few. when i first went to facebook i was amazed how many people are there but werent online before.