Feedback for plugin: acts_as_readonly

All,
  I'm just announcing and looking for feedback for a quick little
plugin I wrote: acts_as_readonly (http://github.com/kevincolyar/
acts_as_readonly/tree/master)

Some info:

ActsAsReadonly

Why not use ActiveRecord's readonly!() feature while fetching the
record instead?

Readonly <> immutable in memory in my opinion. I don't see why you
need to raise exceptions for column assignments as long as they are
not stored back to the database.