This is something I've pondered for a while, but I'm too much of a whitehat SEO person to bother with trying any such tactic. There are many sites that are no longer online. The domains are available for registration and the old content can be found in Archive.org, but it's not indexed anywhere else. Therefore, would that not mean that the site hosting it before could just re-register the domain, set up a new site, and include that content? I know all the leg work is required to rank it still, and from ground zero, but would this not serve as a good base to start from in some cases? Maybe for PBN creation purposes? Now, here's another variable to consider: what if someone were to just steal content from Archive.org, by going to old websites and jacking the articles that are no longer indexed and used them for their own site? There might be cases where the old content is still indexed but it could get removed since the site is now offline -- it's a simple request to Google to do so. Really, and please justify your answer, what lines are there to stop someone from using these tactics and how would Google be able to pick up on any negative factors? Do you think there's a content archive within Google, with the power to check originality against old, previously indexed works?