If data upload to arcgis.com fails, the process has to be started again. This can be frustrating when large datasets are being uploaded to arcgis.com as the process can take many hours even with a good data upload speed. One example is uploading aerial imagery that will then be cached in the cloud. The size of the dataset was 18GB but was failing overnight. The only option was to start again and hope the upload completed.
My idea would be to have an upload manager similar to the download manager on the customer care site that is used to download the Esri products. If the connection is dropped, the machine goes into hibernation mode or the machine needs rebooting, the upload can then be restarted from where it left off.