I didn't think it can happen but it has. Google services has been supplemented by other Web services other than Google's own webapps. After all, Google can't insist that it be kept on Android. Otherwise, Android can't make the claim that it's open, right?
But with Microsoft providing services on Android, or Yahoo, can it work as well as Android with Google? And would you buy an Android device san Google?
I think we may well see more and more Android devices with Yahoo or MSN services over the next year. Personally, I equate Android with Google. And the Web browser will still be Webkit based, which isn't something Microsoft really supports.
But be prepared. Carriers are free to make their own Web service deals regarding Android. With Android-based phones, customization is built in. Depending on the deals made, you may end up seeing Yahoo-powered Android instead of the traditional Google search and mail.
Would you be open to using Yahoo or Bing search? Yahoo Mail or Hotmail?