I'd say the advantage of share buttons using the proper canonical tag is it strips away user-customizations, tracking information (utms), and other info. So fo

I'd say the advantage of share buttons using the proper canonical tag is it strips away user-customizations, tracking information (utms), and other info. So for instance if a user clicks the "comments" link on a blog post, it won't then skip the article when people view it. Though I can also see downsides. For instance you might click on a specific version of a product on an ecommerce site. If you share it and say "I love this version!", that information could be lost in the process.