Amy Hoy doesn't say you should use adwords, does she? Correct me if I'm wrong as I've only read the free chapters and watched the video, but she basically tells you to find a suitable group of customers, see what kind of product they need, and create it. Also, blog about things which that group would find interesting, like 37signals does, to connect with these customers.

Now after reading this article I wonder whether this can actually work. Can you not make a living by creating a product and getting some sales from your blog + SEO?