Space Junk

Humans have been launching objects into orbit since the late 1950s and not everything that goes up does come down.  The area around the Earth is littered with bits and pieces of satellites, rockets and other debris from over half a century of space exploration.  Some of these pieces collide with other satellites increasing the hazard of near Earth travel even more.

Luckily, there are a number of plans to clean up the mess.  Some of them seem to have a decent shot at success, provided funding can be found.  Mental floss has a roundup of these.