Although it was reported that the rebels had BUKS I believe it was thought that they were still under the control of competent Russian operators - obviously they were not. It was known that the rebels had hand held SAMs but these were not seen as a threat to civil over flights, hence the considerable numbers of over flights. The insurance market would have withdrawn cover if they had even the slightest idea that a shoot down was possible.
Shooting down an eastbound civilian jet at FL330 does not, to me, seem like an accident, unless the BUK crew were peasants in uniform with no formal training or knowledge of geography, i.e. trigger happy rebels.
SIA do not usually appear on the front of the crash comics. Be interesting to see if SIA offer some kind of support to MAS, though I doubt it would go as far as the old alliance of the sixties, Malaysia and Singapore Airlines, MSA.