I'm not going to flame anyone for feeling something! Besides, I'm hungry, and I wouldn't therefore want to flame the person holding the cake 
But, I totally agree with Kew. I understand far more where Isis is coming from than MP. I'm also fascinated by family history, how my ancestors lived. And honestly, I'm not adopted so I can't say for certain, but I think if I were adopted, I would not be very interested in my adoptive family history past a generation or so. I would love to hear a story about 'how mum did such and such and couldn't sit down for a month afterwards!' But I wouldn't be interested in greatgreatgreat anythings, because that wouldn't affect me any. It would be my biological family who would interest me. Where they came from, what interesting characteristics anf features they had- all things that make me, me in other words. Sure, environment hs an impact, but genetics plays a very big role in who you are
And I guess, the way I see it is, no one asks a small baby if they want to be adopted. They just have to be, and are expected to deal with it, and expected to just graft from one family to another with no issue. But it's not as simple as that, because, although you can't predict how they will feel as an adult, some people find their genetics hugely interesting. And aside from that, their biological mother is the one who created them, who they bonded with for at least nine months, and who they probably share quite a few core characteristics with (not always, but quite a lot of the time)
It's not that anything is missing from the relationship with their parents. It's that knowing where you come from is a basic human right, and it's one that you adoptive parents can't give you. I can't show my kids where they got the eyes from. I can't give them that. Their biological mother could. She can provide something i never can. I cannot be their bioliogical mother, I cannot replace her. She cannot replace my relationship with our kids. She cannot be the mummy they have had. I can provide their basic needs such as food,m warmth, love. But she can provide a basic right that I can't. And in that way, we complement each other - we are not in competition. I never want DD2 and DS to feel they would have to choose between us - they can have a relationship with two mothers
Now, if DD1 wanted to go back past her biological parents, and do some family hisotry research, i would happily support her. If she wanted to meet them, i would be very upset and feel very hostile. That is NOT anything to do with how i feel about reunions in general, its to do with her situation. Why would she want to meet people who abused her so badly? (she doesn't. She's scared of them, and hates them pretty much)
But in general, no one can be loved by too many people. I believe almost any woman who gives birth is a mother (excpetions for those who abuse their children horribly) Same for any adoptive mum (same exception as before). Two mothers, who must learn to share that title, and come to terms with that. And hopefully, if any child would come to their AM and ask for help, they would be helped and reassured, because ultimately being a mother involves putting aside your own feelings for your childs fulfillment and happiness (no one has the right to tell you how to feel in the first place, but you have the respnsibility to take care of how you express that. On a safe forum is a good place IMO) :)