There is a great post on http://www.bruceclay.com/ about why having structured URLs is a good thing. One of the main reasons I started this blog was to have a place to keep great SEO advice. I´ve always had the beleif that SEO is full of myths, overcomplicated techniques and spam. It can be difficult for someone starting out or even someone who has experience but hasn´t bothered to keep up to date, to know what works and what is a waste of time, or worse still, harmful to their website.
Having a URL structure is so important for SEO that I´ve used it on all my websites since 2004. Ani Lopez really does a good job of listing the 3 obvious reasons to use sructured URLs. You can find them in his article http://www.bruceclay.com/blog/2012/01/structured-urls/
In addition to his three I would like to mention that structured URLs also give these additional benefits:
- Keywords in the URL. Whether it´s a relevance factor or not who knows but I´d rather be on the safe side.
- A nice URL structure shows Google you care. Possibly they consider it a quality factor.
- People can see where on your site they are going (or linking to).