One of the things Arena.Net is touting about Guild Wars 2 is the new dynamic event engine. In theory it means some things happens in game (the events) which can trigger other events.
For example, you’re happily running around when you see a bunch of bandits attacking a farm. If you succeed defending the farm, you can trigger an event to attack the base of the bandits; if you fail defending the farm, you trigger another event to take the farm back and rebuilt it.
In the end, it makes you feel like the world is alive, that you’re an important cog of the “big picture” machine, that you’re actions in that fantasy world are worth it.
There is even a nice Reddit post with the nice things about the effects of the dynamic event system.
But I must say I’m kinda worried about it.
One thing that crosses my mind is the way large guilds can “play” the dynamic events system (in the bad way). Say, someone realizes that winning triggers event B, winning event B triggers event C (or that you need to win both event A and event B to trigger C) and so on, till the large event in the game. A large guild can split their members to beat the smaller events and then push their way to the last event, with everyone. Sure, they can’t stop other people from joining the event ‘cause there is no “parties” as we know from other MMOs, but they can control when those events will happen.
I bet deep down Arena.Net thought about it, but it seems something like that would ruin the fun for most people.