Lots of funny stuff about shooting it down misses the interesting question of how to get it up. At 65,000 the air is so thin that any lighter-than-air object has to be very extremely light. After the weight of the envelope and the helium (yes, helium weighs, too) there isn't much capacity left for the radar gear, solar cells and propulsion system. The wind up there keeps blowing the thing away, so it has to keep flying, and storing enough power to keep going at night is a huge challenge. DARPA and the Air Force have been looking for ideas on this, but I haven't seen any published solutions.