Regarding light pollution: It's not as bad as it seems, since the satellites really only show up while they are raising their orbits, and usually only during dusk and dawn. Once they're in their final orbit you can't really see them. Also, SpaceX are working on the problem. They are testing a sun screen that will block light from reflecting towards Earth while being far enough away from the satellite to prevent overheating.

Regarding space junk: These satellites are in low orbits, so if the satellite breaks it will just re-enter the atmosphere and get burned up within a few months or so. I believe they also have a deployable drag device to intentionally de-orbit the satellites at their end of life, or if there's a problem with the satellite.