Add ancestors note

docs/api/en/core/Object3D.html

@@ -428,7 +428,7 @@
 		<p>
 		callback - A function with as first argument an object3D object.<br /><br />
 
-		Executes the callback on all ancestors.
+		Executes the callback on all ancestors.  <b>Warning:</b> Do not add, move, or remove the object or its ancestors while traversing.
 		</p>
 
 		<h3>[method:null updateMatrix]()</h3>