[Update: This paper has been published as the Silverlight Security Overview. -Nick]
I updated the white security overview white paper for the Silverlight 4 RC release. Biggest change was I've added a section on security recommendations for trusted apps. Other than that it was fairly minor edits, a typo here (eg. Assembly.Load -> AssemblyPart.Load), a rephrase there... Again, all suggestions & feedback welcome.
The original post gives a little more context about the paper.