I've seen some sites and apps where videos float on page scroll. Pretty recently, Facebook website rolled out this feature and received a bunch of complaints from its users. I don't know if this is how the majority of its users feel or it's just a vocal minority.
The YouTube iOS app does this as well - particularly the main video page where the video sticks and floats up top as you scroll down to the comments section.
Some hate this feature and argue that when users scroll down, it's indicative that they no longer want to see the video so why float it? But for most people, wouldn't you normally hit "Stop" if you no longer want to watch a video before scrolling past it?