WTF. Seriously. It works with 1.9 now though.

spec/support/no_id_on_object.rb

@@ -1,5 +1,9 @@
 class Object
   def id
-    raise "You have called id on a non-ActiveRecord object."
+    if self.class.ancestors.include?(ActiveRecord::Base)
+      super
+    else
+      raise "You are calling id on a non-ActiveRecord object. STOP IT."
+    end
   end
 end