Reply #10: You should see the entire list of potential threats [View All]

including our friend 2004 MN4:

http://cfa-www.harvard.edu/iau/lists/Dangerous.html

and the list of those that approach Earth the closest. Guess who is on top of the list, and look at the one that approaches a year earlier:

PHA Close Approaches To The Earth

The following table lists the predicted encounters by Potentially Hazardous Asteroids (PHAs) to within 0.05 AU of the earth from the start of this year through 2178. Objects with very uncertain orbits are excluded from this listing, as are recently discovered objects whose orbits have been computed without consideration of planetary perturbations. The distances quoted are from the nominal orbit solutions in the cited references and can be quite uncertain, particularly for one-opposition objects. Perturbed orbital solutions consider perturbations by eight major planets (Mercury to Neptune), three minor planets (Ceres, Pallas and Vesta) and treat the earth and the moon as separate perturbing bodies. For comparison, the mean distance of the moon is 0.0026 AU = 384400 km = 238900 miles. (1 AU is approximately the mean distance of the earth from the sun = 149597870 km = 92955810 miles.)

http://cfa-www.harvard.edu/iau/lists/PHACloseApp.html