Econet was used in a classroom setting to connect a room full of BBC Micros to a single floppy disk drive. This was an important capability because in those days, a floppy disk drive cost in the ballpark of the price of a computer, so one per computer would have been unreasonably expensive. I suspect this was the main thing Econet was used for in practice.
As far as I remember, security was on the honor system; everyone just saved their file under a different name; there was nothing like a login procedure, no technological barrier to reading, modifying or deleting other people's files. And indeed the cost of implementing security with the technology of the day would've been nontrivial, and if I were designing the system, I wouldn't have paid that cost when the expected use case would have all users in the same room.
But obviously that was a long time ago, and memory is fuzzy, so I'd like to make sure: do I remember correctly? Or was there some form of security that I have forgotten or did not encounter?