Thats by design. ACS wont expose user data from windows live. You can directly integrate with windows live using
Live SDK 5.0 for more control with client side scripting or you can use
If you want uniform way of authenitcation system on way is to write a custom STS wrapping the login functionality.
You can configure custom sts in ACS. so that you would achieve uniform way of authentication for your web site.
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