The scope of this discussion includes only adoptions where birthparents make a conscious decision to place their child -- NOT when the decision is made for them by a child welfare agency. This is NOT the "drug-addicted slut" stereotype that was waved around on discussion boards after the study was published.1. What responsibilities should adoptive parents have for their children's birthparents, both before and after relinquishment?
A-parents must accurately portray themselves and what degree of openness they can commit to. Once they commit, it is only ethical that they abide by their agreement, whether or not it is a formal, written contract.
A-parents also should use only respectful terms when talking with the child about his b-parents. This is not only morally right toward the b-parents, but necessary for the child to know that his origins are worthy. Denigrating the b-parents denigrates the child.
2. What responsibilities should the Adoption System have for
birthparents?
In Adoption Utopia, expectant parents considering adoption get neutral counseling about both parenting and adoption. Some adoption agencies actually provide this, and a-parents should use one that does (there is enlightened self-interest for doing so: b-parents who don't feel victimized by The System are more likely to heal and move forward, which is better for all involved, especially the child. "Stuck" is not good.)
Adoption is only ethical if the birthparents place with full information and no coercion. All resources for how to parent must be presented.
3. And how does the "best interest of the child" fit in with
these responsibilities?
Granted, it's too early for me to tell yet since my children are still young. But one of the reasons I decided not to put a divide between me and my children's birthmoms was so that HoneyT and R-guy would never feel like they had to choose sides. There is no choice to make if we are all on the same side.
I hear from people adopted in the 60s that they could never search for their b-parents because of the sense of disloyalty to their a-parents. Why would I want to inflict such a burden on my child -- in order to satisfy your natural curiosity about your medical history and genetic makeup, circumstances around your birth and relinquishment, and to know how it feels to be around people who look like you and have similar mannerisms -- in order to get answers you're going to have to betray me? They can be true to themselves without being disloyal to me.
So we keep in touch with Crystal and Michele. When open adoption was just theory to me, this was a calculated move FOR my children. But in reality, I have gained a very close friend in Crystal -- someone I thoroughly enjoy being around. Channels are open with Michele, too, and I would love to spend more time with her.
In Adoption Utopia, every woman in a crisis pregnancy for whom parenting is not a viable option would find the people who long to parent a child. They would be truthful with each other and be true to their word. The child that unites them would suffer only from having too many people love him/her.
WELCOME EACH NEW DAY! Just When Your Children Are Fit To Live With, They Are Living With Someone Else! 
Thanks for letting me know about the post.