ArcGIS Online has no backups or versions of data which makes the potential for full blown data loss large. This should apply to feature services so they can be rebuilt from an earlier version if they go corrupt or have issues, and this needs to be for other data types such as maps, apps, and any other fields that have been uploaded.
All ArcGIS Online users are paying for a cloud system and should have access to cloud type features such as backups.
