I've been investigating the og:url tag and canonical URL's tonight in an attempt to wrap my head around the best practice for this.
We've usually always use the node/NID as the canonical URL as well as the URL used for facebook likes. It seemed natural since my idea of a canonical URL is that the URL is persistent. A URL-alias changes if the node title is altered.
However, after getting in SEO/Sharing-trouble with a website that uses node/NID as canonical URL as well as the og:url BUT also uses Global Redirect module (redirecting node/ID to its alias) I'm having second thoughts.
Facebook doesn't like it when the og:url isn't the same as the URL that was liked (see this).
What is the best practice here, considering a use case when you want to use metatags, clean urls, and perhaps also global redirect?