[ResourcesTree.mxml]
<mx:Canvas xmlns:mx="..." width="400" height="300">
<mx:Script>
...
</mx:Script>
<mx:WebService details.... />
<mx:Tree id="_tree" change="{dispatchEvent(event)}"/>
</mx:Canvas>

Outside of my Resources tree, I don't want anyone to be able to access my tree component. However it's automatically compiled as public.

Say I want to add an event listener to the tree change event, I want to force people using my component to listen to the ResourcesTree, not the sub-component.

For example:
var myResources:ResourcesTree = new ResourcesTree();
myResources.addEventListener(Event.CHANGE, onResourceChange); // GOOD
myResources._tree.addEventListener(Event.CHANGE, onResourceChange); // BAD!

private function onResourceChange(event:Event):void
{
  trace("yay captured");
}

This is important for following standard OOP practices. I can't encapsulate my custom MXML components and protect their inner workings. It would be nice for components to allow public, private, protected and etc.