I needed to do some custom validation of fields on a form. So, I decided to use #element_validate. One of the fields I was validating appeared a bit strange to me, though. When I displayed its
$form_state['values']['field_face_palm'] information I saw that it looked like:
$field_face_palm['und'] = 'you_knucklehead'
instead of like:
$field_face_palm['und']['value'] = 'you_knucklehead'