You can fairly easily hide from a search engine by essentially doing reverse SEO techniques, by blocking crawlers or feeding them different results, or just hid

You can fairly easily hide from a search engine by essentially doing reverse SEO techniques, by blocking crawlers or feeding them different results, or just hiding behind login screens. The problem with the similarity technique is that it can find associations between sites that do not link to each other, regardless whether and how they try to hide. It's enough that someone thinks they are related.