I did google: http://www.brcpo.com/bureaucracy/index.html
If they have to keep us from knowing the address unless we send them money burningman is over. Ruined. Kaput. Ashes...Any mail sent to the playa should be addressed to a person with a camp name and (ideally) camp street address, Black Rock City, NV 89412 (new address is only available to BRCPO sponsors at the moment). Festive mail for campers can be sent in regulation envelopes to the Black Rock City Post Office, where the outer envelope will be opened and contents delivered if possible to the inside addressee.