I presume you mean SEO (Search Engine Optimisation) rather than SSO (Single Sign On). Six years ago I launched a boutique search engine which downranks pages which contain adverts on them (the theory being that this would remove the incentive for creating spam) and of course contains no adverts itself (to avoid what Brin & Page described as being "inherently biased towards the advertisers and away from the needs of consumers"). Since then some other search engines have used this approach, or even gone further such as using the uBlock origin score in ranking.