@Rananim:
The NTSB does not have the authority to correct anything in aviation (or, to my knowledge, in any other form of transportation). The Board is not a regulatory or rule-making agency -- it is not an agency at all.
It functions in an advisory capacity, and makes many RECOMMENDATIONS concerning regulation and the like. Those agencies with actual authority (in civil aviation matters, the FAA) may follow those recommendations in whole, in part, or (in many cases) not at all. There is a long history of tension (to put it mildly!) between the NTSB and FAA, that is well known to those who follow aviation safety issues in the United States.
@BBK:
You have it correctly -- in accident investigations, the NTSB quite purposefully refrains from allocation of blame, guilt, etc. It is not a judicial or quasi-judicial body. The goal of accident investigations is to make findings of probable cause, to the extent that available evidence and analysis support such findings. Sometimes, the result of an investigation is that the Board cannot determine a probable cause. Frequently, there are multiple causes, or more typically causes composed of several factors that acted in concert to contribute to the accident.
[One exception to the "no blame" principle: when the NTSB has previously recommended regulatory changes, and find that a new accident might have been prevented had their recommendation been followed by the regulatory agency, the Board is not necessarily shy about pointing this out!]