Why are we so blog-happy here at the Business Buzz (a.k.a. Work Technology) blog? Maybe because blogs are such fascinating business tools, and there's such a big debate over whether they're even worth the time.
In laying out their pros and cons, many folks leave out an important "pro" stated by Rafe Needleman, who sits atop all us work technologists at CNET: a blog is a great way to keep yourself organized, to force you to think about what you need to highlight about your business, and to do it in a public way. Even if only a small handful of customers see it, you're still a business that faces the public, and the blog lets you put that foot forward--and lets interested parties try to step on it, if they want.
I also think there's something organic about blogs. Over time, as Jeff Jarvis has argued, they can force you to organize your thoughts, figure out where you stand, and hone your thinking on what's truly important.