Currently, publishing a map in arcgis online forces us to make underlying feature services (ie : a layer created from shapefile) also public. A public feature is automaticaly visible/usable by other users.
So "sharing a map" = "sharing underlaying features" = "rendering them available for any user of arc map (view / download)".
It's very bad for private / confidential layers ! Giving it to everyone (i.e. viewed in arc map and then downloaded / copied) is not acceptable.
Please allow us to render feature services public (in order to make the map public) without publishing them to all ESRI users : add an option to "block" the sharing.
PS : please excuse mispellings, i'm not native english speaker