I have not been able to find out what the motivation was for the current behavior (I think this is
the initial commit), so I'm interested to know. It seems to me that any attempt to update a readonly attribute is probably the result of a bug. For example, a form may be exposing a readonly attribute (and then incorrectly reporting that the attribute was updated). I'm sure there are cases I haven't thought of though. When is it necessary to allow attempted updates to readonly attributes?
I realize that we cannot just change the current behavior. Does Ben's suggestion of adding an option on attr_readonly seem reasonable?