I have already said it somewhere, but there is no harm to say it again. The most "credible" explanation about why the world will end in 2012 is the so-called "galactic alignment". It is said it will focus a beam of
gamma rays to the Earth and fry everything remotly looking like a life form. This might just be true... except that the beam isn't so much focused, and because of that we have already mostly entered it more than 2 years ago, and last time I checked we haven't fried yet. *checks again* Nope, not yet
About solar flares, we took really strong ones in the face during the recent years, and the worst they did was wreaking havoc with satellites hardware, causing various temporary malfunctions and reboots. Most of the satellites are still operational, and the world is too. Well, sort of
A few years ago, we might have experienced what could really have been the end of the world, when a star about 50 000 light years from us went super-nova. Like strong solar flares, it caused some disturbances in the satellites, but should had it been "only" 40 000 light years away, we would have been all dead as the gamma shockwave would have vaporated our atmosphere

This one however wasn't predicted, and why should have it been, since it wasn't the end of the world either

And to avoid any ill-prophetized end-of-the-world occurrences based on this story, scientists have checked that there is no such soon-to-explode star in our vicinities (but the
Nemesis doomsday scenario will probably continue to roam around).
Anyway, I guess that GhostATR is right: ignorance is what appears to be the most dangerous in this story...
The real sign that someone has become a fanatic is that he completely loses his sense of humor about some important facet of his life. When humor goes, it means he's lost his perspective.
Wedge Antilles
Star Wars - Exile