I have a polygon Feature Layer in the ArcGIS Online Portal that has labels. The labels will display fine if nearly the full feature is within the extent of the map view. However if I zoom in the label will disappear. If I pan to roughly the center of the feature, I will see the label, but anywhere other than the center I will not.
This can be demonstrated by using the states map service.
If you create a Feature Layer using this service, label it using the name at all scales, then add it to a .Net Runtime (100.6) Map, once you zoom in to around the City level the labels disappear. The same thing happens in the AGOL Map Viewer, and various Map Templates.
How can polygon labels be displayed so they show at all scales, if you're not looking at the centroid of the polygon?