Matt Cutts is a google spam engineer. This video is a presentation of Whitehat SEO tips for bloggers, presented at the Wordcamp 2007 conference.

Best take away for me is the difference between dashes and underscores. Apparently google can't split muilti words in the URL eg SEO_workshop and considers it SEOworkshop, however it can split on dashes. Hence create your URL .../SEO-workshop.