I vaguely remember seeing a small help text on YouTube when you try to share an unlisted video where they tell you as the user that it's unlisted and to "be mindful" about sharing it. I think most people who read that don't understand what that means so maybe that's why I believe they don't show it anymore. I wonder if it has anything to do with that `si` URL parameter that the Share button introduces into the URL.
Anyway, maybe I didn't fully comprehend your article, but it still seems a bit mysterious to me how a database of unlisted YouTube videos could exist. Is it just based on user submissions? If so, how are they finding the URLs to the videos in the first place? In my experience, the way they might leak is if the uploader mistakenly adds an unlisted video into a public-facing playlist, but that doesn't seem to me like it would be a common error among content creators.
Anyway, maybe I didn't fully comprehend your article, but it still seems a bit mysterious to me how a database of unlisted YouTube videos could exist. Is it just based on user submissions? If so, how are they finding the URLs to the videos in the first place? In my experience, the way they might leak is if the uploader mistakenly adds an unlisted video into a public-facing playlist, but that doesn't seem to me like it would be a common error among content creators.