If you add a form element of type machine_name and the source element for the machine name element is defined after the machine name element itself, notices are thrown upon submitting the form:
* Notice: Undefined index: #id in form_process_machine_name() (line 3293 of /home/mrbaileys/workspace/Drupal-7-HEAD/includes/form.inc).
* Notice: Undefined index: #id in form_process_machine_name() (line 3306 of /home/mrbaileys/workspace/Drupal-7-HEAD/includes/form.inc).