A. I don’t know how often agents read blogs. It depends on the agent. Newer agents tend to be more proactive about a lot of things. They’re reading literary journals and calling writers; they’re out there LOOKING for clients who can create books and make money. Established agents not so much.
But this whole subject is a lot simpler than you think. Create a blog; build a platform; show the world something interesting and unique. An agent may never come across it and offer you representation – but that doesn’t matter. If they don’t come to you, you just go to them! If you’re not one of the chosen few who is “offered immediate representation,” then you can just create a nonfiction book proposal and SHOW them your idea and platform. Voila.
A lot of people ask about this very thing – agents “discovering” writers online through blogs and such. This happens, sure, but you can never COUNT on it happening. And frankly, I think that you have to have a SUPER popular blog and most people either have a small blog or a medium blog as opposed to a very large one.
If you’re looking for an example of a huge site that turned into a book deal, look at I Can Has Cheezburger? (LOL cats). If you’re looking for a decent-sized blog that was unique and attracted an agent’s attention, this site called Bent Objects is genius and caught the attention of my agent, Sorche Fairbank.