> "Collisions are proportional to the square of the number of things in orbit," McDowell told Space.com. "That is to say, if you have 10 times as many satellites, you're going to get 100 times as many collisions.
Unfortunately, any collision also increases the number of things in orbit, by breaking up spacecraft. The collision between Kosmos-2251 and Iridium 33 generated 1,300 pieces of debris in orbit. The collision between Object 48078 from Russia's Zenit-2 rocket and China's Yunhai 1-02 generated 37 known debris objects, and likely a lot more smaller untracked objects.
This is likely to lead to Kessler Syndrome, a chain reaction of collisions once the density of debris fragments above a certain weight passes a critical density:
http://aquarid.physics.uwo.ca/kessler/Critical%20Density%201...
Unless satellites are brought back to Earth, the likely path of development is that Earth will get a layer of satellite debris which makes a a good part of satellite technology basically infeasible (and any spaceflight much more dangerous).