How many satellites could fit in Earth orbit? And how many do we really need?

The number of satellites orbiting Earth is rising fast, thanks to private companies such as SpaceX. But just how big will these "megaconstellations" become? And what problems might they cause? In the last five years, the number of satellites orbiting Earth has more than doubled and will likely double again within a similar timespan, thanks to the efforts of private companies such as SpaceX. But while these spacecraft can provide important benefits, they are also causing multiple issues that are only just being realized by scientists. More

(Source: Live Science - May 31)