"liveroles:Validated Live Users" is security group like "NT_AUTHORITY\Authenticated Users" but contain only users that enter valid email address. You can use it like other security group when you want just users with validated email allows to do have permission on something.
Windows Live Authentication will not give site developer any email address for its privacy policy. see Username, email and UID of Windows Live Web Authentication
Shetab Windows Live Authentication for SharePoint get user's email address after sign in and use email confirmation system to validate user's email. see How To identify Windows Live ID users and give permission to them?