It seems that the lesson is, if you're going to be a spammer, use a separate IP for each site, use a separate ID for registering each domain, and make each site

It seems that the lesson is, if you're going to be a spammer, use a separate IP for each site, use a separate ID for registering each domain, and make each site sufficiently distinct. Then, if Google decides to ban ALL your sites, they have a hard time figuring out which sites are actually yours. That's the danger of shady SEO. It's an arms race between Google tweaking their search algorithm, and people looking to exploit flaws.