Whenever I hear this question (or someone turning this question into a statement) I'm always reminded of this quote from Only the Paranoid Survive by Andrew Grove:
"Is the internet a big deal? Or is it an over-hyped fad?
I think it is a big deal. I think anything that can affect industries whose total revenue base is many hundreds of billions of dollars is a big deal."
I wonder how Andy would answer this question about blogs -- I'm guessing the answer would be exactly the same.