One of the Laws of Online World Design. I personally like the first one:
"Any general law about virtual worlds should be read as a challenge rather than as a guideline. You'll learn more from attacking it than from accepting it."
Many people believe the mutual defense theory that communities and player towns formed for the common defense. Live together or die alone and all that junk. While there is some merit to the idea, I would argue that it alone won't create strong communities for the very simple reason that there is no way to win. Since we are quoting Koster:
"Someday we WILL be able to hand over the reins of policing to players. But right now, neither players nor developers are ready. I can't tell you how much I wish that in UO we had found a way to make the players able to do this, actually able to win against the bad guys--because I do regard those grief players and those rampant PKers (be they the "good" ones or the griefy ones) as the bad guys in this virtual world, far more so than the monsters. One of my biggest disappointments in UO is that we never found a way to have the good guys win. "
First of all, I voted to keep Trammel.
One of the reasons UO was an incredible social experiment way ahead of its time is that there are no rules. Ideally, with such a land that's free of rules, people band together to defend the weak without the need of policing. The failure of finding a way to do this is also why our castle dwelling spaceman deemed it a sort of failure.
My humble views differ. UO is very much different from other MMORPGs that offer PVP. There's no sanitized avenues/arenas for players to pit their skills against another in a balanced manner. Instead it's a free-for-all grand melee.
Unfortunately, it means that for safety, pks hunt other players in organized groups. They are more successful in finding prey than anti-pk's. They just go to dungeons and chances are that they will find other players in singles or small groups. With their normally superior numbers, there are high chances that it will turn into a gank fest.
Now, consider the anti's, who organizes a party in reaction to reports of pk activities. By the time they can react, the pk'rs would be gone. Bereft of their primary prey, there's nothing for them to do. Maybe hop through the dungeons in hopes of bumping into the pk's. But it's more difficult for them to find pk's.
Meanwhile, there are other other griefers. Like blue pks that goad others into attacking them. Thieves that prey on everyone. Others that lure monsters into attacking others or even gate monsters. The bounty system doesn't work, since pks would just have their guildies kill them to the bounty.
Winning gratifies people more than losing. No one likes to lose all the time. Save for the hardcore pvp'rs, other players would prefer to not have their miners attacked without provocation and killed. The results of their labour in the past couple of hours looted. Most of the time, their characters are not geared towards that. Similarly, if for some reason the pks incurs a penalty upon initiating an attack that is severe enough to guaranteee their defeat in the hands of a miner every single time, they would not pk anyone. (this is of course unfair, but I am just stating a case).
I do not look forward to have my stuff stolen unless it guarantees I can kill the thieves and loot them dry in turn. I like to win too.
And these are still legit aspects of the game. Imagine griefers luring and gating monsters into a room of newbies.
So in the absense of the victims' gratification, most prefer not to participate in a game where they keep losing and thus retreat to the safety of Trammel.
Fel is an aspect of UO, but it is not for most. Same thing for shards with the Seige ruleset.
One interesting idea I thought of, instead of a pvp toggle, what if the initiator's attack will be ineffectual until their targets retaliate first? That should provide a penalty for the rampant pks and a measure of safety for crafters. Of course, there needs to be a timer, once it runs out, even if the defender doesn't retaliate it will become a free for all. This should allow the policing of scripters. Also needs a method to prevent people from abusing this to deny access to areas or resources.