Facebook announced to developers today that they are moving to a 64 bit user ID in November (see below). At 32 bits, the current ID allows nearly 4.3 billion user accounts. Yet, despite having only 47 million users today, Facebook’s move to 64 bits will allow it to have more than 18 quintillion (18,446,744,074,000,000,000) user accounts. Of course, there are currently only about 6.5 billion people in the world. Is Facebook setting their sights beyond Earth or just trying to avoid what happened when Slashdot ran out of space for comment IDs last year. Perhaps they are planning to implement personas. Besides, do you have any idea how much Facebook would be worth with 18 quintillion user IDs? Sextillions…
In any case, I think Facebook may regret exposing user’s public IDs to developers without a one way hash. With the current system, any Facebook developer can get a list of your friends IDs, fetch their names and then store a permanent link to their public profile URL. e.g. http://www.facebook.com/p/fullname/#########. While the public information available there is limited, providing a one way hash to developers would have made this difficult if not impossible.