Finally you will have your username for your Facebook account
From the beginning of Facebook, people have used their real names to share and connect with the people they know. This authenticity helps to create a trusted environment because you know the identity of the people and things on Facebook. The one place, though, where your identity wasn't reflected was in the Web address for your profile or the Facebook Pages you administer. The URL was just a randomly assigned number like "id=592952074." That soon will change.
We're planning to offer Facebook usernames to make it easier for people to find and connect with you. When your friends, family members or co-workers visit your profile or Pages on Facebook, they will be able to enter your username as part of the URL in their browser. This way people will have an easy-to-remember way to find you. We expect to offer even more ways to use your Facebook username in the future.
Your new Facebook URL is like your personal destination, or home, on the Web. People can enter a Facebook username as a search term on Facebook or a popular search engine like Google, for example, which will make it much easier for people to find friends with common names. Your username will have the same privacy setting as your profile name in Search, and you can always edit your search privacy settings.
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.
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.
Think carefully about the username you choose. Once it's been selected, you won't be able to change or transfer it. If you signed up for a Facebook Page after May 31 or a user profile after today at 3 p.m. EDT, you may not be able to sign up for a username immediately because of steps we've taken to prevent abuse or "squatting" on names.
Source Facebook blog