Hiding the identity of the staffs and employees of a whistle-blower organization like wikileaks is something that should be expected. I have never seen anybody who specializes in leaking out information and still walk unarmed or unguarded in the midst of his enemy. US government government particularly has taken a step to ensure that wikileaks reveals the list of its employees.
The only public figure known in wikileaks is Julian Assange. One notable reason why wikileaks is so secretive about the identity of its employees is to ensure their total safety and so as to prevent them from uncertainties. Security of life and property is one cogent thing an employer must take note with total understanding and I think that is exactly what wikileaks has done.
Also by not disclosing their identity, it will prevent the staffs from any form of undue harassment from the government and its security agencies.