I am surely not going to speculate about the actual cause of this tragedy but I have seen several posts saying that it must be somethig terrorist related because airliners do not drop out of the sky like this.
Fact is they do, last years we have had some airliners down due pilot error, malfunctions, weather.... So a terrorist atack is just a possibility among other.
With the information avalaible for this accident, I have just remebered the Indonesia Air Asia A-320 that crashed on the sea after droping from its cruising altitude of FL320 due a combiation of mecanical troubles and pilot error.
Accident Report
I do not mean this accident may have anything with todays tragedy but I would like to point out that other causes other than terrorism could be involved. It has happened before