How to programmatically bring back “excerpts” field in post editor in WP 3.1+

http://wordpress.org/support/topic/troubleshooting-wordpress-31-master-list?replies=14
a few posts down has instructions for default ‘ON’ options

// Change what's hidden by default
add_filter('default_hidden_meta_boxes', 'be_hidden_meta_boxes', 10, 2);
function be_hidden_meta_boxes($hidden, $screen) {
    if ( 'post' == $screen->base || 'page' == $screen->base ) {
        // removed 'postcustom',
        $hidden = array(
            'slugdiv', 
            'trackbacksdiv', 
            'postexcerpt', 
            'commentstatusdiv', 
            'commentsdiv', 
            'authordiv', 
            'revisionsdiv'
        );
    }
    return $hidden;     
}