Asteroid DA14 - big enough to cause a localized Judgment Day for a small to medium sized city - is scheduled to make a close call with the Earth on February 15th, but it's currently expected to pose no danger to life on the Blue Planet.
So why, exactly, are huge chunks of space rock flying around waiting for the right combination of angle and velocity to send us back to the Stone Age? PolicyMic's Michael Suede explains the predominant thesis of asteroid formation:
"The standard theory of asteroids supposes that they are the shattered remnants of planetesimals, 'bodies within the young Sun’s solar nebula that never grew large enough to become planets.'"
However, Suede proposes an alternate hypothesis:
"Enter plasma cosmology. Plasma cosmology takes the approach of including electrical forces within the astrophysical plasma that is present in space. This theory of cosmology was founded by the Nobel Prize winning physicist Hannes Alfvén."
"In plasma cosmology, asteroids are the product of 'electrical discharge machining.' That's a fancy term for lightning bolts blasting rock into space."
Read more about the schools of thought on asteroid formation with Suede here.