Square Enix has announced that they will be merging several servers in Final Fantasy XIV, bringing the number of playable servers down to 10 from it's current 18.
All characters must be designated for transfer before the March 27th merger date, but Square is making it easy to get that taken care of. Starting on March 1st through March 19th, players will be able to choose a post-merger world for their characters to be moved to. If players fail to choose a post-merger world for your characters, they will be automatically designated to a server with lower player count.
If, by chance, when the server merge is completed, two characters share the same name, only one will be allowed to continue using it. This is determined by which active character was created first. Also of import is that all blacklist/friends list information will not carry over during the merge so be prepared to re-block trolls and re-add friends once the maintenance is complete.
For a full list of what to expect in the server merge, you can stop by The Lodestone at http://lodestone.finalfantasyxiv.com/.