With the increase in popularity of self-publishing e-books, I can see how a writer's next natural step would be to seek advice on selling their books. Since this seems like a natural result of having published your book, it seems to make sense to me. While we may not have many marketers visiting, we may have a few self-published writers who can/will share what has worked or not worked for them.
Marketing one's work is a big part of writers' lives these days, and I think it's been accepted as being on-topic for Writers.SE. There are lots of questions specific to people trying to do well with self-publishing, with e-publishing, and also with promoting traditionally-published work (in cooperation with the publishers' efforts, or in addition to them).
These questions are specifically pertinent to writers, because promoting a book has its own unique aspects and challenges (...lots and LOTS of challenges!), that are very different than marketing other products and services.