My favorite technique (in terms of "how the heck did they think of that") is Google analytics referral spam. Spammers use bots to generate visits to your website, coming from a site they own that sells something. You (a website owner) see a referrer you don't recognize sending you traffic so you go see what it is. I fell for it a few years back (granted it was obvious when I visited the "referring" site that it was spam).
It doesn't seem scalable but I guess if you're targeting website owners and able to automate this at huge scale it prob has some success?
I don't think the point was to get visitors directly from those links, but to hope that the referer URLs were ending up in some kind of publicly visible page (e.g. the logs directory of the HTTP website being exposed), have those pages indexed by search engines, and get a URL reputation boost from those inbound links.
It doesn't seem scalable but I guess if you're targeting website owners and able to automate this at huge scale it prob has some success?