Hi,
There is not currently web services for updating content. The web services you see there are built in 3.5 .NET services for authentication and roles, they use the MembershipProvider and RoleProvider so no additional code was needed to use those web services. So far in my Silverlight prototyping I use those services to authenticate and get roles for the user from Silverlight.
It does not yet work on Linux/Mono but if you have a windows box you can experiment and see my silverlight work, or you can try it on the demo site from here: http://demo.mojoportal.com/app.aspx
I do plan to build more web services using the REST toolkit.
Best,
Joe