I'm sure all of you have heard about the 2012 December 21st prediction of the world ending at the end of the Mayan calender. Personally I doubt the Mayans cared enough to set up a calender that far into the future, so I don't really think we need to worry about the world ending. The Mayan's also didn't think the world would end, they thought that a new era would dawn at that time.
What I think is we should be keeping an eye out for solar storms. From what I can glean from the inter-tubes, the sun is on a 22 year cycle in which the influence on our magnetic field waxes and wanes, the last of these events resulted in Canadians without power for nine hours in 1989. 21 years later and the sun is just now starting to signs of this cycle, as of august we have been seeing indications of solar interference. NASA seems to believe the worst of it will hit late 2011 to 2012, at which point we may have worse to worry about then loss of power. Magnetic effects may destroy satellite, scramble computers and down power lines, cutting us off from power, internet and cell phones. Such things may happen once, or be sustained for a year, or longer.
Magnets on large scales have also been shown to affect the human mind, sometimes improving mental functions, so we may be dealing with super humans and global blackouts. On the other hand, this cycle may simply take power away from us for a few hours, before receding for another 22 years.