With the current security model and the fact that we use a separation model in our development methodology, it would be handy to be able to import accounts from one file to another. I'm sure this will raise issues of security but if you have full access on one file and it matches an account and privilege set on the target file this shouldn't be an issue. You would not need to expose passwords, just import them along with the account.
The need arises from having a single point of entry log in file to manage the accounts in our solutions. The beauty of this is that you can leave this file while developing your business logic while the users of the system can be adding and modifying users during the development process.
Obviously this is not as big an issue when using AD. However, many of our clients do not use AD and when we need to work on the log in file as part of the scope of work it can be become a very tedious process keeping the files in synch.