The world was big enough for people to have their little clicks and fights in their own regions. Nearly every city had its 'crew'. Some guild or two dedicated to just ganking/griefing/pking outside of the city. Then that city usually had a crew to oppose them. Then you had your hot spots, most cross roads, some specific dungeon entrances, graveyards and shrines. Then you had your guild spots. Then if you got bored with that, you could just go to an rp zone and kill them off. All the while any point in time would run into people on the way and that would/could lead into another whole adventure. What mostly sanctioned this was player housing.
UO had honest control of the land. I just hope player housing wasn't the main element that kept up those little clicks of players in certain spots, that we too will find those little clicks and spots where you'll always be able to search for some pvp.
Krys Zambre, Cecil Zambre, Aurin - Catskills >D< Draxarum