Comment on How to Increase Blog Comments by Mark.
With regards to point number 4 about no one wants to be the first person on the dance floor, I agree. One of my friends has run large dating sites and he said you need to get a critical mass of people before anyone joins.
He would setup interesting profiles.
Analogously, with blogging having a few online personalities and with interesting Gravatar images helps people start to post. My wife, for example will comment on my website even, and I comment on hers. I get my friends to comment on my website if I write a post that is something that appeals to them.