There are two ways we can utilized this close encounter.
1. We could have tested the Armageddon theory. Where we could have tested the case if another asteroid really came it for a collision course. We could have taken its back, after it has moved to a safe distance away from the earth, tried to disintegrate it. Sure, there would have been several lessons that could have been learnt.
2. We could have sent a probe on its back and could have dropped of at a desired place on its path. As it was pass by Venus or Mars orbits. Not too close, still could have taken to us for the most distance. Considering the fact this asteroid taken about 312 to make one revolution around the sun. This is pretty faster than the spaceships. So we get off mid of the way and set the course to reach mars, which is still on our wish list.
This could have been on the options, but also given the fact that this asteroid was recorded only a year or two back, it would have been a very tight deadline project that could have been accepted.
Any ways, I thought it would have been fun to blow that rock and see it on a live stream :) It could have fed the news channels for weeks.
Image courtesy of Idea go at FreeDigitalPhotos.net