Should I structure my site using subdomains or subdirectories?

I’m interested in finding out how Google currently views subdomains — whether there’s any difference between a site structured as a group of subdomains and one structured as a group of subdirectories. Bob, Somerville, MA Have a question? Ask it in our Webmaster Help Forum: groups.google.com Want your question to be answered on a video like this? Follow us on Twitter and look for an announcement when we take new questions: twitter.com More videos: www.youtube.com Webmaster Central Blog: googlewebmastercentral.blogspot.com More resources for webmasters: www.google.com