If there is any fuel left in it, NASA's probably waiting for the right time to do a retro burn to put UARS in the Pacific. That, or they're letting the Navy test out a new ASAT system on that bus-sized target in the sky. Perfect way to make the Navy look like heroes: NASA projects that the debris will fall over India, so the Navy shot it down so the junk burns up and saves the country. Plus, it'll damage China's military ego by showing them that we can shoot down their little spacecraft if they do anything "funny."