This PW article poses the question, "To Blog or Not to Blog?" Although the piece is aimed at authors of children's books it definitely applies to all authors. I disagree with the author's middle of the road stance on this. She answers the question, "is it worth it?", by saying, "the answer seems to be a qualified maybe--or maybe someday."
Wrong!! If you're an author, or plan to become one down the road, you should absolutely, positively have a blog. Can it become a significant time investment? Sure, but you can invest as much or as little time as you feel it deserves. Don't let that scare you away. Just jump in and do it. That's what I did over two years ago and I'm glad someone pushed me! (Actually, two people pushed me: Robert Scoble and Shel Israel.)
Here's the most important quote from this article: Editor Julie Strauss-Gabel says, "Blogging is a long-term endeavor, one that builds and sustains a loyal fan base over a career." Well said.