Looks like there’s another addon that automates communication with other users.
This addon will alert other players using the same addon about the location of enemies. You can also create lists of players who you want to track, and possibly to gank repeatedly/indefinitely:
it looks like it may be particularly intrusive as hunters and druids can track humanoids and this information will be shared with non-hunters/non-druids via the addon.
edit: sadly, it’s been a couple of months, and it seems we’re stuck with this addon that provides an advantage to those who use it, against those who don’t.
I’ve seen quite a few videos posted of world pvp where this addon is being used, particularly by large guilds that like to gank or harass others.
So my suggestion is that casual players on PVP servers may want to use this addon, and ideally join a large guild that can help you avoid high level gankers in the zone who may already know about your presence due to their use of the addon.