BK wrote about YouTube in the Notes: "I’m trying NOT to go down that rabbit hole, because there are thousands of these videos."
The whole process of YouTube seeming to "know" what other videos a viewer might be interested in based on what we've previously watched IS pretty amazing, though.
One of the most recent". On the day HHW was talking about TV themes, the videos YouTube would offer me following the first five or six theme song videos I'd watched all (or most of) the way through were most entertaining - and when I'd watch those the site would send more and more of them in the recommendations. That was most welcome - although some of the times, the follow-up recommendations are not as welcome.