1. Divide your users into to chicken and egg categories. Build an egg plant! Build a website that allows eggs to show up and is useable without any chickens and add the chickens latter. Often times your eggs are a niche user or geography.
2. If you're going to pitch bloggers and they have no idea who are you already, it probably is a little late to start trying to build a relationship.
You need to target bloggers, who look like they might be up and coming. I'd even target a specific niche. Basically, go to them, and say, "If I can get six of you signed up, I can then get awesome rates from people interested in your niche." Now the hard part: deliver! Once you got all six on board, I'd spend everyday on the phone, e-mail reaching out to the major and minor players about how they've got to advertise with these up and coming trusted players in the niche.