Currently you can share a page with Internal users or any arbitrary e-mail address with the assumption that the receiver will in some way have access to the page (either because they are a user with permission, or because the page is public).
It would be useful to have a feature that is similar in nature to Google Drive's "Anyone with the link" visibility settings on a document. This would allow a page to still appear hidden from anonymous access (through the normal friendly URLs), but would build a unique (obscure) link so you can share the page with a known set of public (anonymous) users.
Adding users just to share one or two "semi-public" articles is costly. I can see many cases where you may not want anyone from the outside world to easily find an article (i.e. general anonymous access), but you would want to provide a direct link to a group of trusted individuals.