Have you considered doing a post on Delegated Authentication?

Thanks,
Don Rule

Do you have any guidance on how to detect when a token is about to expire, and how to redirect them to the LiveID site from within SL?

I only gave a brief overview of the WCF Authentication Service in this article… for some other sweet stuff you can do with it check here: http://msdn.microsoft.com/en-us/library/bb386582.aspx. You could do all your authentication from Silverlight without a single page refresh (well maybe not with Windows Live ID). The aim of this post is to give an overview of how to do lots of stuff in a short time:)

Getting the email from Windows Live ID is a differnt story to authentication – this requires extra permissions from the user(you can also get their contacts etc)… Check out Delegated Authentication here: http://msdn.microsoft.com/en-us/library/cc287637.aspx

The aim here is not to get an email address (after all they could just type it rather than go through all that login stuff). Instead we are using WLID to look after authentication so we don’t have to store passwords and users don’t have to create *yet* another account on your site.