Earlier quoted context omitted.
It could be argued satellite internet is also a natural monopoly / duopoly. How many n-thousand satellite networks can there be? How many companies / countries can afford to launch n-thousand satellites?
There can be a lot. Given the immense volume above Earth, satellite collisions are only a worry because of the speeds that satellites travel and the current difficulty with coordinating them. As the technology for satellite coordination improves (tracking, low-propellent maneuvering, etc), the number of satellites that can fit will keep rising for a long time.
There, every satellite is following the exact same orbit, but different positions around it. There are 500+ satellites on it.
Now imagine how many possible orbits there are. If we could locate satellites accurately enough, we could give every 1 meter shell of altitude to another 500 satellites, giving us 2500000000 between earth and geostationary orbit.