But if you actually want to secure your unique name, you gotta be quick, because:
Starting at 12:01 a.m. EDT on Saturday, June 13, you'll be able to choose a username on a first-come, first-serve basis for your profile and the Facebook Pages that you administer by visiting www.facebook.com/username/. You'll also see a notice on your home page with instructions for obtaining your username at that time.
That's what the official blog says – and what's even more important: once you chose your unique username, it's here to stay – no change of mind later on. And it's first come, first serve – so be quick!
The unique user names must have at least 5 (alphanumeric) chars:
Facebook usernames will be available in basic text forms, and you can only choose a single username for your profile and for each of the Pages that you administer. Your username must be at least five characters in length and only include alphanumeric characters (A-Z, 0-9), or a period or full stop (“.”). While usernames are currently available only for Romanized text, we're looking at how we might support non-Romanized characters in the future.
I really wonder if the majority of users will use their real name, their nickname or try to secure popular keywords. The race starts at 12.01am EDT on June 13th – good luck!