Eric Lawrence tackles the often-misunderstood details of the "deny-read" part of the same-origin policy:

http://blogs.msdn.com/ieinternals/archive/2009/08/28/Explaining-Same-Origin-Policy-Part-1-Deny-Read.aspx

I've never heard it called "deny-read" before.  But I like it.

As Eric points out in the comments, Silverlight has logic in the runtime to prevent applications from using the WriteableBitmap class to read cross-domain content.