Should Canonical be used if your site does not have any duplicate

[ciznerguy]

Should canonical be used site wide even if my site is solid no duplicate content is generated.

please explain your answer

[GrouchyKids]

Hi Guy,

Does this help...

Although the canonical URL tag is generally thought of as a way to solve duplicate content problems, it can be extremely wise to use it on every (unique) page of a site to help prevent any query strings, session IDs, scraped versions, licensing deals or future developments to potentially create a secondary version and pull link juice or other metrics away from the original. We believe the canonical URL tag is a best practice to help prevent future problems, even if nothing is specifically duplicate/problematic today.

Source:http://pro.seomoz.org/tools/on-page-keyword-optimization/new