Drupal Fields Ajax not working
Since the fields were attached via Field API, I have to do this way

$form['field_member_last_name'][LANGUAGE_NONE][0]['value']['#ajax'] = array(
    'event' =&gt; 'blur',
    'callback' =&gt; 'get_suggestion_by_name',
    'wrapper' =&gt; 'suggestions_by_name',
    'method' =&gt; 'html',
);