Welcome to the Q&A Forum

But if it is like Pete said, I don't understand why e.g. SEO Moz has a Canonical Tag on this Page

http://www.seomoz.org/blog/canonical-url-tag-the-most-important-advancement-in-seo-practices-since-sitemaps

Which leads to the exact same page!?

What is the benefit of doing so?

Regards