Robin Hobb recently wrote an article in which she discussed the apparent evils of authors blogging. You can find the article here: http://robinhobb.com/rant.html
The general gist of the piece is that authors shouldn't blog, and should instead focus all of their creative efforts on writing their fiction. Hobb argues that blogging steals valuable energy and time and that an author's work will suffer as a result.
First off, let me say I agree to some extent. I - in my writer capacity - have often sat down to write, only to be lured away by the appeal of brain-free internet surfing. I can appreciate that blogging quite possibly presents a similar challenge - "Oh, just a quick blog entry before I start writing" and all that. Fine, I can see how it might become a problem.
But I feel that Hobb misses a vital point. It's alright for her to not have a blog, as she doesn't need one. Neither does George R. R. Martin (even though he does and insists it's not a blog). Erikson, Brooks and Feist don't need them. Why? Because they're all established authors. People will buy their books and spend hours discussing them, regardless of whether they blog or not.
But for new authors, those who are just starting out and have yet to build up large, loyal fanbases, having a blog is a crucial way of interacting with readers. It enables the new author to discuss and promote their work, without being seen to be intrusive (it's their blog after all). It enables readers to ask questions and make comments. It allows the author to get feedback and to answer any points raised. It enables authors to have proper discussions about their work with fans (check out Joe Abercrombie's blog for proof of this).
In short, the blog provides a vital link between a new author and readers that can be fundamental to forging a loyal readership. In this day and age, it's vital to have an internet presence and while a website is all well and good, a blog offers a far greater level of interaction. It can even serve to attract genre fans unfamiliar with an author's work - I visit Pat Rothfuss's blog all the time and I've not yet read his book, but I enjoy reading what he has to say.
This leads on to my next point: readers enjoy reading the views and observations of their favourite authors. When an author posts about the way they work, or the way they think, it gives the chance for readers to get inside the author's head and see how their mind works. If an author discusses the workings of the industry, it helps prospective writers gain a better understanding of how things work. Even if all an author does is talk about their day, it still gives readers an interesting glimpse into the life of that author. People enjoy reading about these sort of things. I know I do, and I'm willing to bet that thousands of others do too.
While author blogs can be time-consuming, if managed effectively they offer a wealth of enjoyment for both author and reader (not to mention all-important publicity for the former), and for this reason alone I suggest that authors should keep up the blogging.