I think Udo has this about right. Were Madonna's motives for wanting to adopt a child from an orphanage in Malawi entirely selfless? Probably not. Was this the best use she could have made of her wealth? Clearly, no. But was she going to do good, on balance, if the adoption had gone ahead? Most likely, yes.
We may be critical of celebrities for the way they use their wealth, but we tend to think they are at least within their rights, even if they squander it. In this case, Madonna was not going to use it in the best possible way, but she was certainly not going to squander it. It would have done some significant good and no obvious harm.
I guess there's no point in feeling sorry for someone as commercially successful and wealthy as Madonna, but at the same time I get tired of all the unnecessary attacks on her character. She's doubtless far from perfect, in exactly the same way as the rest of us are far from perfect. We'd probably all do things that seem odd to most people if blazing fame and access to vast wealth liberated us from our inhibitions. Many people would use Madonna-like wealth far less responsibly than Madonna actually does. Really, it's hard to understand what a lot of the fuss and sniping in the media is all about. Some of it just seems spiteful: it reflects worse on the journalists concerned than it does on Madonna herself.