Guild Wars 2 World vs. World Blog Post

ArenaNet's system designer Mike Ferguson has penned an official blog post dedicated to the game's server-versus-server or, as they call it, World vs World (WvW). It's a pretty detailed and lengthy read so if you're interested in the title it's recommended that you read it in full, but here's an excerpt to whet your appetite:
We dreamed of a game where players could work together to capture objectives on the battlefield, like keeps and towers, claiming them for their guilds, then fortifications before defending them against hordes of attackers. With players from three different servers fighting each other, we knew that we would need a lot of different areas for them to fight over, and we wanted to have plenty of locations for guilds of all sizes to claim as their own. With this in mind, we created a number of different objectives that are designed to be captured and contested by large groups, small groups, or even just a few players.

To provide enough area to hold all these objectives and a wide variety of terrain, we needed to make some absolutely gigantic maps four of them.

We gave each of the three teams a home map called the Borderlands, where they would have some advantage as the home team. We also created a fourth, central map called the Eternal Battlegrounds that has its own unique features, including a massive central keep. These are the largest maps we can make in Guild Wars 2, and we use as much space as we possibly can in order to accommodate over a hundred people from each server fighting on every map.

Each objective on a map is worth points for the team that captures it. We periodically tally the point total for each server and add that total to their War Score, which accumulates over the length of a persistent two-week battle.

Every Guild Wars 2 server competes in battles in the Mists.

At the end of each battle, every team is given a new ranking. Once a battle ends and team rankings are updated, servers are matched up based on their new ranking and a new battle commences. Downtime between these epic battles lasts only a few minutes just long enough for us to tally the final scores, update the server rankings, and create new matches so there's almost always a battle for the Mists going on.