There are a couple of sites that auto-started video and when you scrolled down, automatically did picture-in-picture. In fact I think Facebook even experimente

There are a couple of sites that auto-started video and when you scrolled down, automatically did picture-in-picture. In fact I think Facebook even experimented with it for a while. The problem with those implementations was that the user had no control over which videos, nor the ability to prevent them from displaying. It took a heavy amount of NoScript isolation to prevent it from happening. I always thought it would be useful if someone would write something that put the user back in control.