Facebook and others have their way of monitoring, but it doesn't work that well.
There could be a measure of diversity in retrieved results. Recommender systems could give you several things that are of interest, but they could ensure diversity. They could give you more perspectives and more different things, even if they're less related but have higher diversity, and not rank them very low. They can make this recommender in their systems have more diversity to not give you only one kind of thing, even if you are only interested in that. That might even increase engagement, because the user could find something else they didn't know they might find interesting.