Well, another asteroid went between Earth and the Moon, and was detected after it passed us...

Orbit Simulation Has a nice little orbital simulator to play with. Run it past this weekend and see how close it was.

Then run it forward by days, and check out what could happen to Venus on May 20, 2005; or Mercury on June 15, 2005; or Earth once more on Sept 5, 2011. Then 2021 looks bad for us as well. This asteroid is a busy little guy - threatening us fairly often. This is only ONE asteroid being watched, there are over 500 known ones that are this close, and of those, 6 are expected to pass within 5 Lunar Distances in the next 10 years.

Since the website I originally got this from has dropped the story, here it is again:
ASTEROID FLYBY: Newly-discovered asteroid 2003 XJ7 flew past Earth on Dec. 6th only 150,000 km away (less than half the distance to the Moon). At closest approach, the 20-meter wide space rock was about as bright as a 13th magnitude star and an easy target for backyard telescopes.