Mark this date, Saturday, 13th June 2009, 12:01pm (Friday, 9:01pm, California time). If you are unsure of the timezone, it is OK, just head down to Facebook to see the big countdown.
What is significant is that at the present moment, facebook profile is just numbers. It is difficult for anyone to remember them. Now, with this new feature, it will be easy to find friends. However, you have to be fast as the URL is first come first serve.
I remembered years ago, Friendster did this and I think this is a good idea. But, why so late??