Giving power to the user in front of the screen
Modern desktop computers running Linux have a sort of double personality that they do not usually share with Windows-based PCs. On the one hand, they are used as single-user workstations where the operator is granted full access to the machine resources, and on the other hand they are also real servers.
Of course there is no reason why a network user located far away should have free access to our machine's audio device or, much worse, to the modem configuration.
With Linux rising popularity in the desktop market, we need a way to distinguish the "user in front of the screen" (better named desktop user) from the "user from far away" (better named remote user), and grant them different rights. This is how I solved this problem for my local network of double souled computers.