The canonical tag is simply a way to silence webmasters.
Yesterday at SMX West it was announced that Google, Yahoo! and Live have agreed upon a method to help webmasters define original content within a site. The canonical tag is a meta tag used to tell search engines which page to list in SERPs when multiple listings of the same, or very similar content exist in their databases.
On-site duplicate content has been a big issue since the beginning of the web. There are lots of things that could cause search engine spiders to index the same content at multiple locations. URL canonical variations (http://www.exmaple.com vs. http://example.com) is the most common issues, but there are others. This is a good explanation of the canonical tag and how it’s implemented.
In september the Google Webmaster Central Blog published a fairly extensive post on how search engines handle on-site duplicate content in hopes of dispelling a lot of the rumors and speculation circling the issue. Despite how clear the article was, and all the other resources on the web, there were still LOTS of questions about the issue.
As new webmasters come into the space trying to understand SEO and mitigating duplicate content the easy thing to do is ask Google. If you’re site is set up correctly duplicate content shouldn’t be an issue. The canonical tag, is not the end-all be-all of duplicate content. You still need a sitemap, good URLs, redirection from the www or the non-www to the correct path, etc. This tag is simply an easy answer to the duplicate content question.
What do you think? Have you implimented the canonical tag yet? Is it really THAT important considering all the other things that still need to be done?