If this turns out to be terrorist-related, (still a big 'if' at this stage), those who are opining that the terrorists are 'breaking the usual rules' by not claiming responsibility probably should remember that the terrorists 'broke the usual rules' on Sept 11th 2001. Anyone old enough to have been in Aviation pre-Sept 2001 will recall the "don't resist, co-operate in every possible way" rules that were universal in every airline (with the possible exception of El Al and Korean Airlines) until the events of that Tuesday changed everything.
If this is terror-related, maintaining silence is proving remarkably effective, particularly while the wreckage remains not located. The mainstream media will eventually lose interest if nothing happens soon - (it would probably be a very different situation if 230 Americans had been involved, but let's not go there) - but the SAR effort will continue, downgraded, but in some form - and a considerable expense - until something is found. And then the real expense will start, particularly if a deep water recovery is involved.
Someone's said it before me - this could end end up costing a lot of governments and as many airlines huge amounts of money. Which means it will end up costing us, the travelling public, huge amounts of money as well.
If terrorists are involved, the aircraft - or more likely its wreck site - could be many thousands of miles away from the current search area.