I don't think the video ad example is particularly unethical, assuming it's disclosed to the video uploader. Or at least it's no more unethical than ad tech is by definition (which is pretty unethical, admittedly).

This domain registration scam is more like https://en.wikipedia.org/wiki/Front_running and https://fortune.com/2016/04/20/amazon-copies-merchants/, i.e. inferring from the inside information you have as the market maker/platform that the value of something is going up, and using that knowledge to make trades or business decisions that are profitable to you, not something a platform is normally expected to do, and costly to the source of the information, i.e. your customers. These are considered unethical/illegal because the possibility they might happen is not disclosed to the user of the platform.