We expect Facebook Platform to scale quickly in the upcoming years, we are making some significant changes to support this and thought it would be important that you know about ahead of time. We want to do big things!
Up until this point, all of our user IDs have been small enough that 32 bits is sufficient to store them all. In the not-so-distant future, we will begin using 64 bit object IDs in some places. So, the numbers will become to big to handle in some situations.
In particular, if you are storing IDs as INTs in your MySQL tables, it will be important to alter those columns to become BIGINTs.
We expect this to happen in early November, and hope that this heads up gives you some runway to make the necessary changes.