In Visual Studio 2010 there is a handy tool for managing users for my Silverlight Business Application. How do I do this with my deployed application?
Sorry to say, but you will have to write user management code in your app.
You might find this article interesting.
https://web.archive.org/web/20210306174425/https://www.4guysfromrolla.com/articles/052307-1.aspx