Facebook has just announced that it will be offering custom usernames (“vanity URLs”) for Facebook Profiles and Pages, starting at 12:01 a.m. EDT on Saturday, June 13, 2009. 

Custom usernames are a big deal for many Facebook members, who have long been frustrated by hard-to-remember Page and Profile addresses made up of random strings of numbers. Directing people to your Facebook page can be as easy as telling them your username.

For organizations who want to publicize their Facebook presence in a radio PSA, television ad, or printed brochure — by any publicity method that requires people to type in the URL, instead of simply clicking a link — the advantages of username-based URLs will be immediately obvious.  And having your organization’s name as a prominent part of your Page address should also help with the search engines.

Each Facebook user can claim one custom username for his/her personal Profile, and administrators of Facebook Fan Pages can claim one username for each Page they own — with certain restrictions. 

Most of the rules and restrictions around Facebook usernames are aimed at preventing the kind of unethical “squatting” that has happened with domain name registrations from time to time.

To qualify for a username, your Facebook Page must have been live on Facebook with a minimum 1,000 fans as of May 31, 2009.

For personal Profiles, only those who created accounts before 3 p.m. on June 9, 2009, will be eligible for a username.

New users will have to wait until after 12:01 a.m. (EDT) on Sunday, June 28, 2009.

This decision was made to prevent people from creating new accounts just to take advantage of reserving a username. We’ve also reserved certain names that have been brought to our attention in an effort to help third parties protect their intellectual property and other rights.

...Facebook reserves the right to remove and/or reclaim any username at any time for any reason.

Facebook provides a form you can fill out to reserve your trademark, even if you don't plan on using it for a username yourself, to ensure that no one else can claim your trademark as their username. They have also set up a complaints process to follow if someone else has claimed a username that you believe infringes on your legal rights.

When choosing your Facebook username, here are a couple of points to keep in mind:

Usernames must be at least 5 characters long, and can only contain alphanumeric characters (A-Z, 0-9) or a period (“.”) Usernames are not case sensitive. Certain generic words such as “pizza” and “flowers” (and no doubt certain rude words, too) are not allowed as usernames.

Once you click “Set Username,” the username you’ve chosen cannot be changes, edited or transferred to a different Facebook account.  Think long and hard about what username you’ll want to have attached to your Page or to your personal Profile for the rest of your time as a Facebook member — and type it in carefully.

When an account is deleted, that username will not be made available again. Facebook does this for security reasons. This may be an inconvenience, and will certainly lead to a rush on usernames by people with names like “John Smith,” but if you think about it you’ll see it makes good sense to protect the reputations of Facebook members who might leave the network in future.

For more information, see Facebook’s special FAQ for usernames.