The Mayans believed that in the year AD 1999, mankind would have 13 years to recognize our own patterns of self destruction. Then, starting December 12, 2012, our entire lives would be tested and only those most in touch with their spiritual sides would survive (as some interpretations have it). Many people take this as a sign that a natural or manmade disaster will occur, tearing apart the civilized world and taking us back to hunter-gatherer days.
There are other interpretations too: from sun storms to the eruption of a super volcano; from a magnetic field reversal to a meteor impact. Some people even point to the Large Hadron Collider in Switzerland as the bringer of doom. While the world may come to an abrupt end any time, any day, without warning - one thing is for sure: our modern society, like all civilizations before us, is geared to postulate over end-of-the-world mysteries with gusto.