Here in South Africa where we have so many Aids orphans and vulnerable children you get cases of white families that adopt black children. It's not common practice, but it's not unusual either anymore to see white parents with a black child or children. White lesbian couples, also adopt black children.
I sometimes wonder if inter-racial adoption is a good thing or not, I have certain reservations, but ultimately I do think it's a good thing. In South Africa there is not a strong culture of adoption among black families - this is something that child welfare organisations have been trying to change. So if people are willing to adopt, it is more than likely going to be a white family. Sometimes they adopt because they can't have their own children, but it's just as common to have white people who already have their own children to adopt a black orphan.
The main reservation I have about inter-racial adoption is that due to circumstances the black children that are adopted end up losing all contact with their own culture and heritage, they speak English and are unable to speak any African languages. I think this must be pretty hard to deal with growing up, and I'm sure that it would affect your sense of identity, and self-image and lead to a lot of painful questioning and soul searching.
On the other hand there's a part of me that feels it has to be better to lose your culture, but gain a loving family, a degree of material comfort, stability and an education. Surely in this regard, it's better to have love and security and lose your black African culture and language. I don't know what the answers are, ideally it would be great if you could still have both - and are able to educate the child to speak their own language - maybe in school, or by a private tutor (and take lessons yourself). But even so, they wouldn't really be part of their culture. Unfortunately, the reality in South Africa means that it usually ends up being an either/or situation, and black adopted children end up not being able to speak their own languages.
Somehow though, growing up in a difficult family situation myself, I can't help feeling that love and security wins the day. If you grow up with love and stability, you have a better of chance of gaining the tools to deal with cultural alienation. The alternative is to grow up with nothing at all, no love, no education and a life of poverty.