gistfile1.js

var Driver = {
  add: function(event) {
    event.stop();
    
    $(this.get('rel'))
      .insert(Driver.template(this))
      .subNodes().last().show('fade');
  },
  
  remove: function(event) {
     event.stop();

     var item = this.parent('.item');
     var delete_field = item.first('input.delete');
     var options = {};

     if (delete_field) {
       delete_field.value = 1;
     } else {
       options.onFinish = item.remove.bind(item);
     }

     item.hide('fade', options);
   },
  
  template: function(element) {
    return window[element.parent('.nested').get('data-template')]
      .replace(/NEW_RECORD/g, new Date().getTime());
  }
};

".nested .add_nested".on('click', Driver.add);
".nested .remove_nested".on('click', Driver.remove);