My interest in this is to hide the location of other players/mobs.
Having battlegrounds where you have no idea where the enemy is.
Mostly that involves getting rid of the radar and overhead map; possibly toggling off the onscreen-waypoint-monitor.
It would also be great to disable the /ui action cycleTarget* commands to prevent players tabbing through enemies, or at least making it LOS.
I also see a lot of possibilities for the server being able to remove a single-player dot - /stealth abilities for smugglers, /conceal for riflemen (as mentioned by the OP), pets with a phase-shift ability.
So, for the "area" effect it could just be certain areas of a map/certain cells that cause the maps to disappear, or it could be players in a group, or players "registered" for an event.