public function getExceeded($user_id, $existing = null)
    {
        $limit = $this->getLimit($user_id);

        if (empty($limit)) {
            return array();
        }

        if (!isset($existing)) {
            $existing = $this->getList(array('user_id' => $user_id));
        }

        $count = count($existing);

        if (empty($count) || $count <= $limit) {
            return array();
        }

        return array_slice((array) $existing, 0, ($count - $limit));
    }