Use a parameter `feature.enabled` to enable/disable a feature through configuration. And then wonder why you still see the menu item, even if you have no `feature.enabled` parameter at all.
`Yii::app()->params['feature.enabled']` returns `null` if the parameter is not defined. But in this case that's different from `false` because `CMenu` uses `isset($items['visible'])` which returns `false` for `null` values.