Not everyone believes in the whole 2012 thing, there are many realists out there that see it as just another example of human gullibility. Most that do believe in it does so because they think what they have heard is true and doesn't bother with looking up the facts. Another reason seems to be that people want to have something to fear.
Never heard of Amsterdam, but I've heard of Nostradamus. He didn't predict anything that has come true. All the things that people say has come true are things that they have found after the fact, not before. If you do that you can find predictions that has come true in any longer writing, all you have to do is to decide what to look for and then twist the facts until it fits what you want it to say. Easy. So what you have there is predictions made by other persons not Nostradamus.
The same thing goes for the Mayan calendar. The End of the world bit is the opinion and prediction by Josè Argülles not the Mayans themselves.
The end of the world has been predicted for thousands of years now and we're still here. Christians has predicted it since 44 C.E. and this far they have not been right.
The world will keep on existing, even after all humans are gone. So it's not really the end of the world that worries people, it's the end of human kind and I think that it will be a long time before anything (including us humans) manages to kill off all humans in this world. Things will change over time of course, but we are very good at surviving.
Personally I think that the end of the world is our own death. That's when our life here on earth ends, the end of our world as we know it, and there is no point in worrying about something that will happen to us all in due time.