[RedTyger]

I wouldn't be surprised if SEO urls are considerered less and less important by search engines in the future, if not already. They have little if any genuine relationship to content substance, have nothing to do with quality and are comparatively easy to implement site-wide without any improvement to your content at all. Considering how search engines are trying to discount or at least minimise factors like that, they'd be crazy not to take it into account. In your example (showthread vs football etc) all the URL does is add the keyword football, plus a few others, to the URL. What search engines are really interested in - the content - has nothing to do with it. Keywords do are taken into account when linking, but what percentage of that is the URL itself and what percentage is the link text? I'm willing to bet you that it's very strongly weighted in favour of the link text, not the URL itself. It doesn't make a lot of sense to do otherwise.

What Lizard King said is true, the document and the content itself are what SEO is really about. Nice URLs look nice but they're really such a small part of what it's all about.