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Apophis (2004 MN4) is the one to watch, because its first close approach is coming up much sooner, in 30 years (2036) -- which is I think a comfortable amount of lead time to actually develop some nifty program combining a long baseline of Earth observations with some little mission. For example, you could impact Apophis with a transponder, and track it really accurately.
That's great, but I'd much prefer it if we could impact Apophis with several pairs of spacesuit boots. 30 years doesn't seem like too short a time to plan -- if we started now.