I think one of the salient points here is that it must be an independent body who investigates any accident/incident and publishes it's findings together with their conclusions.
As a pilot the incident which comes to mind was around the time of Lockerbie when a BA 747 was involved in a near incident at LHR. As I recall, due to pressure on AIB and the fact that there had been no loss of life etc., there was no formal inquiry yet the Captain was taken to court and it was then up to a jury to make a decision based on technical aspects rather than the findings of AIB etc. (As an aside, subsequent to this incident the Captain concerned committed suicide, sadly).
I actually believe that any accident is a product of the "system" and it is unfortunate for those on duty who are involved. Can you put your hand on your heart and say that the training you received was perfect in every respect, that the equipment you use is faultless, that the environment you operate in is perfect. The answer is often no, yet it is you that may end up carrying the can. Another thread running on PPrune lists concerns of First Officers who do not want to make waves concerning certains Captains who violate the Company rule of No Smoking on the Flight Deck. There are still some organisations around where personnel are afraid to raise issues for fear of repercussions and yet they are the people who are in the front line should anything go wrong.
I know I have rambled on a bit here but it concerns me that in many walks of life where safety is an issue staff seem to be under more and more pressure to perform on a continual basis. I can work in overload for short periods successfully but not all the time. Incipient amendments to legislation as a result of harmonisation of rules across the EC do not give me cause for encouragement.