Do you think open adoptions or closed adoptions are better for the adopted parents and the child?

Lately a number of states have begun to advocate open adoptions, meaning the information about the adoptees Birthmother and Father would be known to him later. Can you see why an adoptee might really want to know where he or she came from? Or do you think it would be threatening to the adopted parents? Which ype of adoption would you elect to do if you had a choice?