This is a really _excellent_ description of `object_double`; nice work!

One other use case that might be worth mentioning is doubling an instance of a class that heavily uses `method_missing`.  IIRC, I originally thought up `object_double` when you were documenting how to use the verified doubles feature for `ActiveRecord::Base` subclasses, since it uses `method_missing` so much, and the idea came out of that (as if you have the class loaded, using `object_double` seems preferrable to the other work arounds such as defining column attribute methods).  Do you think it's worth mentioning something about this use case as well?