There are things humans naturally just don't want people to know about themselves. I, for some reason, never had a problem sharing that kind of information.
Then, there's the things that not even you want to know about yourself. Those would be the worst because, if you'd rather not know them, why would you want anyone else to? Yet, you have to find a way to let them out. Let out those things that probably are what truly make you you.
That's when a completely anonymous blog comes into play.