I swear, everybody gets the cool news before me: an asteroid named 2009 BD was recently discovered, and it appears to have an orbit that is very similar to Earth’s. I could go on and on about resonances and horseshoe orbits and co-orbital debris, but you can read all about it at AstroProf’s page and Universe Today. And I still have nothing in my email inbox about it. Grrr.
The asteroid is not in danger of hitting us, and is only 10 meters across anyway. Something that big hitting us would explode high in the atmosphere (maybe dozens of kilometers high, depending on the composition of the asteroid; rock is fragile and it would detonate way up, but iron would get down lower before exploding) and rain down debris over some unsuspecting area – probably the ocean, given that’s 70% of the planet – but that’s about it. And again, this one won’t hit us, so don’t panic.