Are they really? How many times have we seen an adopted child taken away from the only parents they know, who cared for them and loved them as their own and returned to a "birth parent" who obtained a good lawyer or father who crawled out of the woodwork?
The system isn't perfect but in my opinion the only solution is the complete destruction of all documention relevant to the child's parents as well as that of the persons who chose to give the child a loving home.
Another suggestion is that the documentation be sealed, and only given to the child when he/she turns legal age.