Good point. Either shot down or terrorism seen to be the most likely. It it not often planes break apart over the ocean on their own
.....with all electronic communication going out at once. That is the key point that leads me to believe it is terrorism.
While most airline crashes happen during or shortly after takeoff or during a landing or because of bad weather, it is not impossible or out of the question to suffer a sudden and catastrophic failure of some kind at altitude and or combined with pilot error (see Air France Flight 447).
Aside from a sudden failure of the electrical systems, Im also thinking of some sort of a rapid depressurization due to a failure of the integrity of the plane, i.e. metal fatigue.
http://en.wikipedia.org/wiki/BOAC_Flight_781
http://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243
While it is way too early to rule out any cause including terrorism, Im not about to jump on a plane crashed ; it must be an act of terrorism bandwagon.