Would LDAP be a good solution where you are running a service and want to have flexibility and ease of expansion? Imagine that you provide email, web, and file storage services and that a machine for any of these is no longer enough. Particularly when it comes to email and file storage, at some point you would need to have more than one machine to accomodate either service and so a centralized way of keeping track of users would be necessary. I have recently heard of LDAP and want to know its PROS and CONS particularly in a Linux setting (Debian or whatever it works best on) and possibly a windows setting. Are there any other good (and perhaps Open Source) options?