Why do you blog?

As I'm gathing my thoughts and creating yet another seminar on the power of podcasting and blogging, I'm musing over how exactly best to define and capture the uniqueness of blogs in just a few minutes. Podcasting I can go on and on about, but blogging seems so, well, intuitive to me that I'm having difficulty taking the step back to explain the whys and wherefores. In short, I'm feeling Amy Gahran's pain over creating two-second statements for conversational media!

A good place to start, perhaps, is what blogging isn't. Seth Godin wrote about how a blog is different from a website--not a bad starting-point if the audience is familiar with websites but thinks that "blogs" are  impolite sounds diners make after dinner.

Of course, if I follow the two-second statement philosophy, the definition should be not so much a definition but a benefit statement--as in, what can blogging do for you? I'm thinking that focusing on the question, "Um... yeah... Heidi, but why should I blog?" will end up with a nice, succint, personal benefit for would-be bloggers.

So... why do you blog?