It's always been a bit of a pain to play with foreigners: ping rates are high, games lag, and they have different, strange customs, but ArenaNet are throwing caution to the wind and finally allowing us to play with those fellows who aren't from round here. Bucking the MMO tradition of locking you into a single region, ArenaNet are letting you play on any server you wish. I shall attempt to summarise their lengthy explanation of how they've done this below:
That and they've delineated the world into three distinct areas: Europe, North America, and other. Each region has a vast datacenter designated to manage all the traffic generated from the players around the world. Yet despite these designations you'll only be restricted by this region lock when activating your game. You need to activate the game in the region where you bought it.
As ArenaNet put it: " We do this to support our local retail partners, and we use this information to connect you to your optimal data center, customer support team, and to ensure the correct language support." From that moment on, though, when you go to pick your home server you can pick whichever one, from whichever datacentre, that you want.
In the early days you'll be able to transfer between the servers for free. Though as the populations begin to settle down then server transfers will be limited to once a week. There'll also be a cost you have to pay in in-game gems to move to a more densely-populated server. Though there will be a free "Guesting" service that lets you play on a friend's server for free. There will be restrictions to this feature: for instance, not being able to take part in the World vs World events.