"we run out of safe orbits in which to put things without them getting pulverised by tiny bits of broken satellite."
Thanks for that. One of the big problems right now is all of the un-trackable junk that's been shed from all of the launches over the years from Sputnik on. I recall a very large British satellite that one day just quit with no notice at all. It's still in orbit as dead as a post. The hypothesis is that it was hit with something very small going very fast that took out something very critical. The orbit was ever so slightly disturbed so it wasn't hit with anything very big.
The impact to visual astronomy from the Earth is already being seen. The impact to radio astronomy is going be be very large. If even a small number of radios on these satellites misbehave, it can mean big problems. The Voyager probes send their signals back with a 6W transmitter. Rovers on Mars can send directly to Earth with equally as tiny amounts of power. The big radio dishes that receive these signals are plucking the signals from deep into the noise and the last thing they need is a cacophony of porn and cat videos making the job harder.
Won't it be fun to send astronauts back to the moon through a needle's eye of window between these satellites? What do China and Russia think of "American" satellites blanking out the sky?