Facebook says more than three million users have already registered personalised web addresses for their profiles on the social networking service.
Instead of a sequence of numbers, users can now create their own unique name, such as http://www.facebook.com/DavidCameronOfficial , for example.
The UK opposition leader was one of those who were quicker off the mark than cybersquatters, who have reportedly scooped Prince Charles, Downing Street, Girls Aloud, Rolls-Royce, Waitrose and Morrisons.
Registration was opened at midnight on Saturday 13 June on a first come, first served basis for Facebook's 200 million users.
Within the first 15 minutes, more than 500,000 user names were assigned and about one million in the first hour, according to Bloomberg.
Security experts have advised that although Facebook does have policies for closing and recovering accounts, trademark owners should register their names before someone else does.