As far as I can tell, anyway. While reading 3rd party documentation1 about our own technology, I often run into links to msdn.microsoft.com that are 404s. I know that internally, we use redirection links when we expect content to move over the course of the lifespan of a product that might need to use it (e.g., for help support), but it seems silly to force publishers to do the same. Should it also be their responsibility, in the case where MSDN does a content reorg and deprecates old content, keep a local cache on their own website to support their own books? It would be seriously nice if there were (1) a way to request a permalink2, and (2) be able to instantly tell whether a URL link was a permalink or an ephemeral link, to know whether or not it should go into a publication / blog post / etc.
2 Or at least one that had a specifically determinable lifetime that the publisher could then caveat in the introduction, or take steps to do the caching I mentioned before.