I mention on my SEO page that having a descriptive URL is a good thing. In the example I say that www.huntsville-bike-parts.com is better than having www.bobsbikes.com. Why?? — You know that incoming links (sites linking to yours) are very important, perhaps equally important is the phrase that links the URL. When you have a descriptive URL, this link and phrase association are one and the same.
For example, here I have linked the phrase Search Engine Marketing to www.marketing-ontheweb.com.