I think the problem in general is that near monopoly services are "roach motels" for data. That makes it impossible for a competitor to come along and use the data you put into a service or platform. I am not talking about all data, I am saying the data that users actively entered into a service: pictures, videos, contact information, relationship status. Make a law that said if I upload data to your service, you have to have an API of a open format where I can download all of it again, and I can give permission to someone to download it in a practical format.

IMO that would do a lot to reduce the monopoly power of social networks and platforms like Youtube, and be fundamentally fair.