Accident investigators have two tasks: one immediate, the other longer term.
The immediate task, following an accident, is to determine whether there is - or even might be - useful advice that should be disseminated to the operators of the type of aircraft that crashed. It's not necessary to be absolutely certain of facts before advising operators to check a component or a procedure if a risk might exist.
The Spanair Boeing MD-82 accident at Madrid is one of those for which the number of plausible causes is almost infinite, given the very sparse data being made available by the investigators. We have been told the aircraft got airborne, but clearly it was unable to stay airborne, and it impacted the ground with a very high nose-up attitude.
At this point, therefore, because of the lack of information provided, intelligent speculation about the possible causes by experts and interested parties - like MD-80 operators - can still include the following: incorrect take-off configuration; de-rated power selected despite Madrid's density altitude at the time and a tailwind of 9kt during the take-off run; incorrect speeds calculated or set; engine failure or of loss of power; uncommanded thrust reverser deployment. Then there are all the potential combinations.
Two days ago Spanish investigators returned from their visit to the UK Air Accident Investigation Branch with the downloaded data in their possession. It is in their power by now, surely, at least to rule out some of that list, even if they are hesitant, at this point, about postulating the primary factors they believe might have contributed.
Accident investigators are public servants. They are paid by the public to serve the public. The information they hold does not belong to them, it belongs to the public. The public is not so stupid it would fail to understand information - even incomplete information - if it were provided.
One of the main problems here, as in most of the world's countries, is that the investigators are taking second place to the judiciary in the investigation, and lawyers do not seek knowledge with the aim of preventing a recurrence of this type of accident; they seek evidence to use to prosecute individuals. Hence the silence, and the lack of information provided to MD-80 operators who need it.