It "will not be possible" for people to exploit the border of no-PvP zones by switching in and out of safety as they please, because of the timer that kicks in upon entering and exiting the PvP zone. That timer controls whether or not a player is protected: Players will remain unprotected for a short while upon entering no-PvP zones and will stay protected for a short while upon exiting them. This protection prevents damage both to and from other players.
Players will not be able to stay in protected areas to farm materials and skip the excitement of looking over their shoulders for a foe every time they pause to harvest a resource node. Safe zones will have relatively common resource and "next to no rare resources." The rarity and value of resources will go up depending on how dangerous the locale is, so players will have plenty of incentive to move away from safe zones.
Get the full word on safe zones and how they're totally not going to be even a bit exploitable at all on the official forums.