At what point does contact with natural parents stop being beneficial?

Although I am all for contact, I have to admit sometimes I just want to drop kick a few first parents for their actions. I have very little to offer except it may be hard for them to see their children growing up in another home. That is not to say anything against you or other adoptive parents, I appreciate people who can see the importance in it. I just wonder some times how I would have felt had I been involved in an opened adoption. I think it could be or would have been very difficult and maybe that hurt is coming out in inappropriate actions. I would talk to them about it and see if you can't come to some common ground, if not, you may have to limit contact.