Hi,

Let's say several external sites are scraping/harvesting your content and posting it as their own. Let's also say that you maintain a single unique/permanent URL for each piece of content, so that content aliasing (on your site) is never an issue.

Is there any value from an SEO perspective to including a canonical link in your header anyway, such that when your site is "scraped", the canonical indication is injected into whatever site is stealing your content (assuming they harvest the raw HTML rather than going in through RSS etc.)?

I've heard different things about the behavior of cross-site canonical links, from "they're ignored" to "behavior undefined" to "it can't hurt" to "sure that's exactly what canonical is intended for". My impression was that canonical was a good way of dealing with intra-site but not necessarily inter-site aliasing.

Thanks~