For folks who publish a map service and then make a map with it in arcgis.com there is this issue. They cannot show a popup on that layer in the arcgis.com web map viewer, if the ArcMap map author has set that layer to have limited field visibility under the layer properties. Currenlty it is impossible to create or show any popup if field visibility has been set in ArcMap. Hopefully either the arcgis.com user can create a popup, or arcgis.com can be intelligent to recoginize field visibility settings, and even an ArcMap HTML popup setting.
