We are currently in development on a new site. Categories (& tags) are pretty much meaningless for us because we've implemented custom posts & taxonomies.
By default, because I have enabled pretty permalinks, if I create a post titled, "Mubarak steps down" without selecting a category, Wordpress will give me this: domain.com/uncategorized/mubarak-steps-down.
Today, I installed the custom permalinks plugin which enables me to make the permalink virtually anything I want. I have a custom taxonomy called countries and one of the terms is Egypt so I re-wrote the above permalink to be domain.com/countries/egypt/mubarak-steps-down. domain.com/egypt/mubarak-steps-down would be better but there's nothing there & writing a re-direct for all countries would be a major pain.
The pros, as I see them, in doing this:
1) A reader may realize that by removing the post title and re-submitting the url in the browser that they will see more content on the parent subject most relevant to the individual post, in this case, Egypt. Of course, this can also be done by making a link to the Egypt section on the page easy to see.
2) I think* it could be an effective white hat SEO strategy for communicating something more relevant in the url than 'uncategorized' or something else generic like 'events' or 'news.'
What are the pros and cons of doing this with respect to WP database performance, etc.?