If you can get traffic somehow, it's worth it. Most people cannot get enough traffic to make it worth it. As merrihiatt said, start with Amazon and Smashwords. That covers the major bases. If sales go crazy (very unlikely but not impossible) maybe you think about investing more time and resources into extending your publishing reach, but for most investing that time in to writing more and more books is the better choice. A (good) publishing business plan is thinking LONG term and focusing on product (books).