One just has to watch how the Netflix algorithm works from a new account to see this in action. It seeds itself with a few questions it asks - what genre do you like? Then it makes suggestions. Once you follow one of those suggestions, it suggests things that are somewhat related (by subject mostly). Over time you land up in a very narrow band of stuff based on what you chose. The star rating system is based on your propensity to watch - though it gives the impression that it is an external rating.
The only way to break out of this narrow band is to ask other people what they watch or hit the search button and find new stuff.
You're right. I had only thought to mention social media, but in truth it is just media in general. Great observation.