So, Blizzard's 4.2 has introduced a new daily zone that restricts flight, attempting to help the game's world pvp crowd. Why new additions weren't made to Tol Barad is a mystery, since that's been the world pvp "hot spot" (or was supposed to be). The previous expansion's Wintergrasp zone saw far more activity and was constantly upgraded, and also allowed flight during the non-BG event.
While the new zone sees some decent traffic, the problem is that Blizzard has implemented a safe zone right next to the starting questing area. By "safe," I don't mean the use of guards, but by granting pvp immunity as soon as a person steps over the line. There is no count down, just raw invincibility, so that people can simply camp the line, attempt to kill people, and jump over to safety when things get bad. This wouldn't be an issue if the zone were more open, but there's a pretty decent bottle neck that may prevent a person from escaping.
The result is, like a decent portion of WoW, a heavy restriction on the ability of players to police their own community. Because people can avoid pvp as soon as it's inconvenient for them, retribution can be close to impossible without zerging and heavy CC, and even then, some classes just can't be stopped if played correctly.
The issue may start to disappear as quests open up deeper into the zone, making it so that line humpers have to wait longer to see their victims, but persistent players will still be able to grief other players in relative safety.