[PLUG] What is /exports/users for?

[John Jason Jordan]

I just discovered that I have a new folder labeled /exports/users that
contains folders for all the currently attached removable devices,
including my NAS. These devices also appear at /media/jjj, as they 
always have. I can write or delete files on these devices from either
location, either with the GUI (Thunar) or the command line.

Why is it necessary for devices to appear in two places? Whose idea was
this?