When developers decide to make a good size portion of their game devoted to PvP there are a couple of key decisions that control the direction it takes. The first decision is about the scope of PvP in the game. Some games that mostly want to focus on raiding have almost no PvP except for small areas that allow players who enter to attack one another. Very boring but sometimes that's all you need, like in the case of classic Everquest. Other games like EvE Online go the opposite route and have large portions of their world available for PvP combat. Still others restrict player combat to instances designed to enforce rule sets on players. Both World of Warcraft and City of Heroes favor systems like this which are often considered the most fair if not the most exciting.
But while the scope decides the type of audience a game will attract the major decision that makes or breaks a game is how the PvP is organized. Developers in the past have chosen to ally players by either guilds, factions, or just to have a free for all rule set. All three are viable and can be fun under certain circumstances. The problems come about when they don't mix well with the scope of PvP in the game. Just to give one example imagine a MMO where the only PvP took place in a few open areas with no rules or rewards. It doesn't really make sense to place faction or guild requirements on players in this game and doing so would just hamstring what little PvP existed. There are other match ups between scope and organization that make even worse sense.
Probably one of the worst things a game can do is to drop players into a MMO with massive open world PvP and no means to ally themselves with anyone. Luckily, Funcom isn't stupid and they made it so players can align with guilds or even play on a carebear server. The problem I see is that a lot of people coming from World of Warcraft are going to think they know what it's like to play on a PvP server. However, open world PvP is very different in a faction based game compared to a free for All one. And while technically Age of Conan is going to be organized around guilds I don't this will really come into effect until the later levels.
I think initially we are going to have a lot of players trying out the PvP servers and then discovering how much having factions softened the blow in World of Warcraft. We'll probably start off with something that looks a lot like Ultima Online back when it only had the PvP shard. Eventually as guilds establish themselves I expect the greifing to become less common place and the game to resemble EvE Online in some ways. However, I think Age of Conan is always going to have some problems that are unique to itself. The biggest one is going to be chat spam I bet since the game has avatar based combat and no factions to restriction communication. Even the regular servers are going to have border kingdoms and capture the flag mini games which will be sure to spawn some trash talking.
I've had cases before in World of Warcraft where I had players from the opposing faction make an alt so they could throw insults at me after a battleground. It was annoying but I could easily use a command and ignore them. In Age of Conan I wonder if the ignore list will be large enough. I expect every gank to be accompanied by a tell insulting my skill and questioning my sexual orientation. I'm sure over time these types of people will be ostracized but they are going to do a lot of damage to player morale in the beginning. The non PvP servers should be less affected but are still going to have the same basic problem.
So why play on a PvP server in Age of Conan if it’s going to be that insulting and ganktastic? Well for some people the opportunities to be a griefer are going to draw them to those servers. Others like myself are probably used to the sense of excitement and the way small scale battles randomly pop up on PvP servers. It's not for everyone and that's why Funcom included normal servers so they didn't alienate everyone. I just want to make it clear that the choice of whether to play on a PvP or Normal server is going to have much more of an impact in Age of Conan then other games.