He was using the mental model of files and folders -- that files exist and refer to stored bytes, and that there can be one or several copies of a file. There can be links to a file that take very little space relative to the file.
I had to tell him that I have no idea what sort of storage model these services expose, if any, and that the concept of a file system backed by a storage device is not the analogy that applications expose to their users these days.
He eventually understood, but I could feel his frustration -- that the mental model he had was really just chosen by a past moment in application design, and that what replaced it is nebulous and disempowering.
