Player versus player, though often politically charged and frequently maligned, is indeed a powerful feature to include in massively multiplayer games. A poorly implemented PvP system can be a real setback, and as great learning is still going on within the early great MMP games, knowing exactly what to do can be difficult. Still, PvP has helped drive at least one MMP to the top of worldwide sales. Our game Lineage has great PvP castle sieges, which helped drive that game to the over four million subscribers it sustains. Without PvP, one of the primary attractions of that game would be lost, and I am sure it would have far fewer subscribers.

I have become a strong believer in what can best be described as consensual PvP. By this, I do not mean a simple PvP, no PvP flag a player can set, but rather a world that has consistent rules for danger and safety and clear demarcations of the areas where both exist. For example, no one in the real world likes to have their home robbed, or be mugged. Thus, in no idyllic virtual existence should this happen either. However, most people know and expect to get shot at when they go play paint ball or laser tag. Most laser tag-type game facilities even announce how "friendly fire" rules are set for that particular game, and players can choose to play or sit that one out based on how much fun they will have in that circumstance.

In my mind a great MMP will be primarily non-PvP, with exciting PvP areas, clearly marked. Those areas could be arena battles, "every one for themselves" badlands, areas of highly valued resources in disputed territory, or castles for the taking. However surprise player killing, which can be fun for the killer, is never fun for the innocent bystander.