It's not neccessarily about code being open source or not: you can pretty much run a wide and large proxy network for any of the services using run of the mill

It's not neccessarily about code being open source or not: you can pretty much run a wide and large proxy network for any of the services using run of the mill free software. This means that to prevent all of the issues, you need a huge overprovisioned network. So to make economics work, you'd have to become one of the largest networks in the world, and thus serve lots of clients, making you again a "centralized" service.