Then it would be very hard to mine for quartz, glowstone, and fortresses if I understand. Lets say only one fortress is found - the people who have claims there have power over who gets there or not. Or if you're strip mining. Long trips out of the spawn area. You would run head on into another persons claim, and have to go around. Another thing would be traps, and pigman farms. People could wander onto the plot, and they'd have a trap set up, and you'd die and lose your stuff, not to natural stupid causes, but because of another player in a non pvp zone. And there are gold farms that can be made, which are usually automated, so that's another reason.
Don't get me wrong here, I'm all up for the idea, there's just lots of things to keep in mind, considering what the server already has, and its rules.