In Drupal 7.21.
http://drupal.org/files/core-7.15-remove-file-attach-load-985642-41.patch
...
@ /modules/file/file.field.inc line 264
// Load the original entity, if $entity->original is not already set.
$entity->original = (empty($entity->original)) ? $entity->original : entity_load_unchanged($entity_type, $id);