From the grapevine....
Someone I know has been asked to write a supposition on what occurred... I note clearly this is complete hypothesis, based on general knowledge of the industry, assumptions and thoughts. I don't have any details on the accuracy of these statements, however it seems feasible to me...
Boeing had issued a notice of stress fractures on the top of the fuselage (around the aerial?). Malaysia Airlines chose to not act on the advice as it was not a compulsory notice.
The supposition is , this part of the aircraft gave way resulting in slow but steady decompression, this also dislodged the GPS and comms for radar identification, thus the airplane 'disappeared'.
Auto pilot, without GPS, did it's best to fly on but slowly and surely dove the plane into the ocean some many hours from it's last known/reported position. Guess is to the East, as to the West it probably would have been picked up again on radar, and/or hit land.
Because of slow and gradual decompression, both crew and passengers lulled into a slow, progressive sleep. The plane flew on for some hours until it hit the ocean and has sunk, some thousands of miles from the current search area.
A hypothesis, nothing more.
Ramjet.