It\'s common practice in MongoDB to use short key names to save space. For example, one might want to use \"fn\" instead of \"first_name\"
However in your app, you\
you should consider using
field :fn, :as => :firstname
as outlined here: http://groups.google.com/group/mongoid/browse_thread/thread/ce3298d6a167bd70
this is a very good practice which is fully supported in mongoid.