What is the purpose of blogging?

Having a blog is definitely the cool thing to do. Let the record show that I had a blog long before the wave hit.

So, what is a blog's purpose? If it is to get thoughts out in written form, then why not buy a journal? They're must be something intriguing about everyone with internet having access to my own thoughts. Maybe this is our 15 minutes of fame...

I've also noticed that bloggers tend to start blogging as some sort of cathartic release of thoughts and emotions, but it quickly becomes consumer driven. The worth and value of a blog is usually equated to how many comments have been made on each post. Is that what this is all about? Popularity? What happens is bloggers post things that will yield the most amount of comments. So, then is it for the reader, or the author?