About 12 years ago I hacked together a "black hat SEO" website using synthetic content. I picked a niche (baking/recipes) and cobbled together a PHP script to generate content based on a keyword list I put together. I found a simple markov chain text generator and had it spit out a web page for each keyword in my list. There were hundreds of static html pages full of keyword rich content. The search engines loved it.

I traded backlinks through a website (whose name escapes me) where you'd place a javascript snippet on the page and it would load 10 random links to other websites. I think you could also pick which sites you wanted your link to appear on and they'd pay a certain price per month to keep it there. It was all about boosting PageRank in Google through a keyword link.

The idea was to create a website for search-engines, not for humans. It was about gaming the search engines and as a side-effect, creating organic traffic to the site where a human would then be bombarded by Google Adsense. The ads were "relevant" to my generated content and keywords.

It only took Google about a month or so to blacklist the domain. I think I made about ~$400 in ad revenue in just a few weeks. IIRC, the threshold to payout your adsense revenue was $1k and I never reached it.

All in all, it was a fun little project that furthered my interest in web development.