Might be controversial, but I pretty strongly believe that buying ads is in the same category of manipulation as altering search results, with perhaps the cavea

Might be controversial, but I pretty strongly believe that buying ads is in the same category of manipulation as altering search results, with perhaps the caveat that ads which declare themselves as ads are maybe not nearly as bad. Ads manipulate the flow of information going to a person for the benefit of the advertiser. It's taking advantage of a vulnerable person in hopes that they will change their behavior - whether that change in behavior is beneficial is irrelevant.