[kelnos]

Aren't you contradicting yourself there? Stack Overflow is ad-supported, but is good. But you want search engines to penalize sites that have ads?

I hate ads, but I don't think we should be focusing on them here. Some sites that have ads have garbage content, and some sites that have ads have useful content. Just... find the useful content, and return it in search results. I know "just" is doing an awful lot of heavy lifting there, but I don't think "has/does not have ads" is as important a signal to a search engine's algorithm as you think it is.