Open pvp is only sustainable if there are
consequences for behaving like a wolf or a criminal. Not that people
shouldn't be able to play villains. In fact, I believe they should be.
But it shouldn't be an easy and risk free practice to go around preying
on weaklings and noobs. If real effort isn't put into making pvp fair
and competitive, it usually dissolves into some sort of gankfest. Pvp
in real life may not be fair, but most mmorpgs are far from any realistic
simulation of real life. And if combat in pvp was really supposed to be
like real life, my character could kill anyone else's character with
one well-placed hit. And that character would stay dead. I could hide an archer up some tree or in the window of an abandoned building and snipe passer-byes all day long.
A villain usually has better things to do then going around waylaying random people, like seeking some kind of ultimate power, plotting world domination, overthrowing a kingdom, or seeking revenge against a hated foe.
The kind of people that like to rob and/or kill for pleasure, profit, or no reason at all are usually described as thugs, gangsters, serial killers, or psychopaths. There are laws and police in place to attempt to restrain the activities of such people. People should be allowed to behave like that if they want to in a game, as villains often need minions to do their dirty work. But the way pvp is implemented in most games, the kind of criminal, predatory behavior often associated with bullies is not only usually without meaningful consequence, but even encouraged and rewarded.
Until games are actually some kind of logical and realistic representation of life, I believe pvp should be considered more of a sport than anything else. Sports have rules in order to attempt to make them fair. People still try to cheat, and sometimes succeed in doing so without getting caught, but few to none would want to play them or watch them if there were no rules at all. I don't think anyone would find a game between Major League baseball players and Little Leaguers to be interesting, unless, perhaps, they are sadistic in some way.
EDIT: Unless it is in self-defense, in the line of duty for a police officer (except in cases where the perpetrator is unarmed or not fighting back), or occurs during legal warfare, killing people is generally considered a crime. I do believe games should reflect this principle. But, "oh, come on, it's just a game", someone may say? That may very well be, but if that's a person's attitude, he or she (usually he) shouldn't expect me or most other reasonable people to want to participate in the predatory fantasies of the gankers.
EDIT #2: My definition of Ganker - Those who aren't really looking for a
challenge in PvP and just want to prey on weaklings and noobs. Or
people that will repeatedly kill the same player-character for no reason
other than that they're there (or someone who has zero chance of defeating them in any case - and
usually the person won't have much opportunity for revenge in the near
future). I think killing should have a purpose beyond the pure enjoyment of killing. But maybe that's just me.
My definition of Unfair in MMORPG PvP:
Losing to someone just because they've played longer, played more hours, or paid more money and have thus become far more powerful than I can hope to be without playing for months or years or paying an equal amount of money. I can compete with people's wallets all day long in the real world if I like. If I haven't played a sport as long as someone else, I probably won't be placed in the same league as them. Unless I am sort of genius or prodigy. To be more precise, I don't want to be an ant fighting against gods because I haven't played as long as someone else. There are advantages one might gain by spending more time with any particular activity, just like in the real world, but they shouldn't make a person unbeatable. I should have a chance of moving up from the Minor Leagues to the Major Leagues rapidly if I have the talent and the skill. Baseball players aren't allowed to use corked bats in games, and they certainly wouldn't be able to use a magical bat that always hit a home run every time they swung at a pitch.
Now if someone outsmarts me or outnumbers me*,
fine, that can happen. Wandering out in the wilderness alone is not the
greatest idea most of the time.
*Or maneuvers better or plans better, whatever. Basically I want things like wits and skill, tactics and teamwork to play a larger part in PvP than anything else.
EDIT #3: My goal with this thread is exploring the possibilities of how an mmorpg could be made into a true role-playing game similar to pencil-and-paper rpgs, without the need for incredibly advanced artificial intelligence or virtual reality. I believe open world PvP is an essential element in doing so. Realm vs Realm as opposed to a free-for-all (though the community a player belongs to doesn't necessarily need to be a kingdom, there can be smaller and larger units), but people could choose to leave their community as well. There are more details and ideas in my other posts. And in the posts of others.