From the New York Times, Feb. 11th, 2009:
Debris Spews Into Space After Satellites CollideThis is a serious and growing problem. You can imagine the worst-case scenario over the long term - that the swarm of junk surrounding Earth becomes so dense that it forms a sort of minefield such that no craft can go into orbit without a significant risk of collision; we will have encaged ourselves with our own debris. That's a remote possibility at this point, but if it came to pass, it wouldn't be the first time we managed to junk a pristine and seemingly limitless environment with our crap.
For decades, space experts have warned of orbits around the planet growing so crowded that two satellites might one day slam into one another, producing swarms of treacherous debris.
It happened Tuesday. And the whirling fragments could pose a threat to the International Space Station, orbiting 215 miles up with three astronauts on board, though officials said the risk was now small...
It happened some 490 miles above northern Siberia, at around noon Eastern time. Two communications satellites — one Russian, one American — cracked up in silent destruction. In the aftermath, military radars on the ground tracked large amounts of debris going into higher and lower orbits.
“Nothing to this extent” has ever happened before, Mr. Johnson said.