Because so many things are unpredictable, ideas commonly accepted will be overturned the next morning. Although I get the feeling that this isn't exactly what's being suggested. Many people are thinking of the physical world itself. In that sense, we are always on the brink of destruction either politically, economically, socially, and militarily. Nothing is for certain and things could easily spiral downward quickly.
It doesn't have to be in 2013 when the world ends. It could end right now, today, this second. We don't know. We don't know a lot of things, not how the universe was created or if Allah or God is real, or what the hell a human truly is. How were we created? Why is the space, space? We don't know.
There is simply no evidence to suggest that any kind of world annihilation will occur any time soon. So many people have predicted the end of times as we know it, but the sun still rises and we go about our daily lives. We should continue to plan on life as normal in 2013.
I believe that the world is not going to end in 2013. This statement has been around for years, with no concrete proof as to why it is being said. No one can determine the end of the world, because it is just not possible. A similar statement was made back in 1999, when the year 2000 was approaching.
Who knows what kind of world it will be, but we will still be here, and we will still be going the way we are going. Sure, there are a lot of doomsday predictions out there, but those happen all the time. I think the Mayan calendar just ran out of space and was showing that time is circular. However, if we don't start making changes, then this world is going to get more socially retarded and environmentally unsafe.