Based on what we have so far (assuming that satelite ping story is true) I belive investigators are working with a few scenarios. It is clear that someone flew this plane off its route. In what circumstances and who did it it is still a unknown to us but we can speculate:
1. Both the pilots did it
2. One of the pilots did it when the other one went to the toilet
3. One of the pax, or more than one, hijacked the plane. You got to consider that the individual flying had some good knowledge about how to fly a jet, disconnect communication systems, fly under the radar etc
4. Memeber(s) of the cabin crew took over the plane and did it.
5. Pilots together with the cc did it
I belive its more important to find the plane at this point rather than figure out what happened exactly.
It amazes me how the malayasian investigators waited a week before searching the houses of the pilots for any clues, signs of foul play. Its not about disrespecting them, its absolutly normal to take into consideration any possibility when you dont know what happened. Thats from an investigation point of view.
Sorry, but before you figure out what's happened, eveyone involved/at the scene is a suspect.