Nate Combs over at Terra Nova has another piece up in his PvP series, this time about EVE Online and the "asymmetry of PvP." In a game like World of Warcraft, the devs have said that they're aiming to keep players as equal-- if you take on another player at your level with your level of gear, you've each got a pretty good chance of winning, and the game is designed to set it up so that you can both show up on a level playing field. But in a game like EVE Online, that plan goes out the window-- players can attack each other anywhere and anytime. There are consequences and advantages to attacking at certain times, and it's up to players to decide when and where PvP works for them-- it's an asymmetric system that leaves it up to players to find balance.
I've just recently starting playing EVE Online, and I can tell you that the system has its drawbacks-- yesterday I had to log off because I had a wartarget camping my station, and if I left, I would have gotten blasted to pieces. Later in the day, I was mining and had another enemy warp in on my location with a much more powerful ship than mine-- I had to hightail it out of there, losing my ore completely. But on the other hand, a complex system like this leaves a lot of options open, too-- if I wanted to, I could buy my own powerful ship, and go and hunt that guy down when he least expected it.