The more organisations that choose to list themselves on the Directory, the greater the value to the Lync community. If your organisation is federated, be that openly or privately, I'd strongly encourage you to list at least the basic information in the Directory.
Similarly, if you know of other organisations that are federated, encourage them to join the growing community of organisations listed here.
The following four fields are all that is required to list your organisation on the directory. New listings will appear on the Directory immediately.
The following sections are entirely optional, though strongly recommended. The more information you can provide about how to federate with you, the more likely other organisations are to be able to find you.