There are many popular issues that you really need to look at their history to understand. The best example of this might be the end of the world theorists. By now the idea that world ending in 2012 is part of mainstream culture: I even get asked about it by 12 year olds. So is there any truth is it? Are we really all doomed as the Mayans predicted? What does history have to with the apocalypse?
2012 is not the first time people predicted the end of the world. One of the more famous end of the world predictions is the Tolendo letter from 1184. This letter was sent to the Pope of the time and said the world would end in 1186. The Archbishop of Canterbury in England fasted in order to try and prevent this catastrophe. Low and behold, the world went on, and so did the letter with different dates, for years afterwards.
Even in my own lifetime the end of the world has come and gone. There was the turn of the century, where people thought that the new millennium would hail in the apocalypse. Then large groups were worried that the Large Hadron Collider (LHC) would create a black hole that would destroy the world. Well, last week the LHC started up with out a problem. So far I don't think the world has ended.
So now the end of the world marches on to 2012. There are all kinds of unsupported ideas on how the world will end, and why. The reality is that 2012 is not special. People who claim it to be the end of the Mayan calendar, just don't understand the Mayan calendar. A really good through description can be found at Universe Today, but the basic idea is that the calendar doesn't end, it just turns over.* So I cannot see how this prophecy differs much in any way for the Tolendo letter.
Someday, the Earth will no longer be inhabitable to humans. Lucky for us we still have a few billion years before the sun makes the Earth into a fairly miserable place. It is possible that an asteroid will come and wipe us out, but we are getting better at finding and tracking potentially dangerous asteroids. Maybe we will develop the technology to prevent such an impact, and then travel to the stars to preserve our species. When I look at the end of the world claims, I see a pattern. The end of the world always seems to be just around the corner, and you know what, eventually they will be right (just be very very patient).
*I'm not entirely sure why the ending of an ancient calendar would signify the end of the world even if it were true.