The orbits of Earth and the asteroid Toutatis come close in December of 2012. According to the Center for Astrophysics at Harvard, Toutatis will pass within 0.04633 AUs to the earth on December 12, 2012. (Forthcoming Close Approaches To The Earth)

Our understanding of its orbit, assuming stability, has it not colliding with the earth. There is always a small chance that the orbit could be changed slightly by gravitational influence of other objects, or even impact with other small bodies.

Debunkers will deny this, but their assumption of infallible accuracy is wrong. Today in The Atlantic we learn that our knowledge in this area isn’t as arrogantly high as we once assumed:

Other scientists are making equally unsettling discoveries. Only in the past few decades have astronomers begun to search the nearby skies for objects such as asteroids and comets (for convenience, let’s call them “space rocks”). What they are finding suggests that near-Earth space rocks are more numerous than was once thought, and that their orbits may not be as stable as has been assumed. There is also reason to think that space rocks may not even need to reach Earth’s surface to cause cataclysmic damage. Our solar system appears to be a far more dangerous place than was previously believed.

In the end, we can’t always be sure of the predictability of an orbit. And also, we can’t track every object, as evidenced by this recent close call: Space rock gives Earth a close shave – this asteroid was as big as Tunguska and crossed by at a height only twice that of geosynchronous satellites.

Read more here: The Sky is Falling.