Last month (October 16th) the third stage of a Russian satellite launcher unexpectedly exploded after it failed to put two satellites into orbit. Launched via a Proton rocket, there was some kind of problem in the final stage and apparently the remaining fuel in that stage caused an explosion. This created a debris field of several hundred new bits of space junk (pieces of the third stage and the two satellites). This prompted satellite (and space station) operators to check their orbits and make adjustments if there might be a collision with this new cloud of deadly (at high speed coming from the opposite direction) debris. On the bright side, many of these new bits of junk are large and in a low orbit, so these will soon fall towards earth and burn up.
The space junk situation is getting worse. Five years ago the United States became the first nation that had to change the orbit of one of their satellites to avoid the cloud of debris created when China tested an anti-satellite weapon earlier in 2007. China had launched an anti-satellite system (a KillSat or Killer Satellite) on January 11th, that destroyed an old Chinese weather satellite, about 850 kilometers up. That's at the upper range of where most reconnaissance satellites hang out. The KillSat hit the weather bird, and the result was several million fragments. Most of the pieces are tiny, but at least 817 are truly dangerous (at least 10 cm/four inches long, wide, or in diameter). There are many such debris swarms up there that have to be watched and avoided. But these other debris swarms are the result of accidents. For example, on February 19th, a new swarm was created because of the accidental explosion of a Russian rocket that put over 1,100 dangerous fragments in orbit. Those two incidents increased the dangerous debris in orbit by about fifteen percent.
The U.S. Terra environmental satellite was in an orbit that indicated a seven percent chance of hitting debris from the Chinese KillSat test. So controllers adjusted Terra's orbit slightly, to reduce the risk to zero. Similar adjustments have become more frequent in the last five years and are expected to get worse as more satellites are put into orbit.
The IADC (Inter-Agency Space Debris Coordination Committee) is an international organization that coordinates the exchange of information, and space operations, as they relate manmade and natural debris in orbit around the earth. Every year some of this stuff falls into the atmosphere and burns up but there are always new accidents or deliberate operations that add more junk to the spaceways.