September the 11th has indeed changed a great deal.
There are however families of irish decent who would never consider divulging information which might identify them and their ancestors.This was well before September 11th.
This is also true for families who live in areas of the world where fueds have existed for centuries. Where even the original reason for the terrible animosity has long been committed to the grave.
It is important to know and be proud of your origins and it can be done with care. The wishes of those of our families who do not wish to disclose living relatives dob and location have to be respected. I agree that there is much in the Public Domain which already is public property but you may provide the vital missing link which is not!
My family were re-settled from Ireland over one hundred years ago. I would love to return but cannot. Friends of mine who did recently and whose families were re-settled at the same time and within the same area of England. Were abused by there own relations in southern Ireland when they tried to discover their roots and have been refused their rightful inheritances.
September 11th has made people aware probably as never before. It does not change the fact that a terrorist of whatever persuasion who is determined, will use any information easily accessible to his or her own benefit. Governments do it as well we perhaps were nieve to think otherwise. Most agents use historically correct information as they do require credible and checkable life stories!
The question of can you be sued by your own family for disclosure will depend on the law of your particular part of the world.A scurrilous prosecution I would expect to fail! Wilfully disreguarding the wishes of a relative or friend may not. Knowingly placing a relative or friend in danger as with displaced Northern Irish expats would not be defendable. That goes for asylum seekers from any part of the world who choose and are granted safe residency in another country. You need to think through disclosure and if there is doubt do not disclose.Dont reply immediatly to emails that purport to have information but request more info than you think is reasonable and do not disclose themselves.As an american policeman once said "be careful out there!!"
best wishes Richard