This is the principle at work in the US bipartisan #AMERICAAct, which would force Google and Meta to spin off the parts of their ad-tech business that put them in a conflict of interest. Right now, #Googbook represents both publishers *and* advertisers, while operating the marketplace where ad sales take place, and they take 51% out of every ad dollar:
https://www.eff.org/deeplinks/2023/05/save-news-we-must-shatter-ad-tech
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