I've recently finished a site, and have been asked to add canonical links to the top of each page. I admit I've never looked into these before.
The site runs on a CMS that has very clean links—there's only ever one URL version. No session IDs, query strings etc. Except that the index page of each section could be called clientsite.com or clientsite.com/index... etc, but I can fix that with a few redirects. I also redirect the non www to the www version.
SO... is there any point in canonical links for this site? According to the video I linked to above, there is the possibility that external links to the site might be a problem. Such as someone placing a link online with some upper case letters instead of the normal lower case... and I'm not sure how shortened links such as tinyurls (used by social media &co.) might affect things.