I would like to see some support for Silverlight from either Moq or Rhino Mocks. That's because I like the way those Mocking frameworks work. I think they both make use of Castle's DynamicProxy, so that's another thing that first needs to become Silverlight enabled.
I'm sure more people thought about Mocking in a Silverlight runtime but didn't find a solution too. I'm interested if anyone started to port one of the above Mocking frameworks to Silverlight. I'm not even totally sure if it's possible but at least a part of Reflection.Emit exists.
What are anyone's thoughts about Mocking in Silverlight?