Sure but I still don't think there is much meaningful difference. Google looks at both your current search/browse activity and gathered data (the gathered data

Sure but I still don't think there is much meaningful difference. Google looks at both your current search/browse activity and gathered data (the gathered data being especially important for all the very many Google-served Ads off of google.com) Facebook also looks at your current search/browse activity and gathered data. The only real difference is Facebook search is universally entirely worthless so far less of that signal gets used relative to more passive snooping.