Monopoly? Last I checked there were multiple competing mobile carriers. You do have to put a lot of capital at risk though to be a national carrier. Which is exactly the point, really. Someone put a lot of capital at risk, and now that their bet has worked out, the regulators want to step in and tell them how to run their business and (in many cases) how much return is fair for them to get from their investment.

Regulation of this sort is the same as partial nationalization, and has the same effect to a measured degree. When people anticipate that the returns on their winning bets will be 'moderated,' or that they will have to set business policies for the 'greater good,' they will in the future make less risky bets or put less capital at risk.