Anonymity is a spiritual principle that is a key part of 12 Step programmes such as AA (Alcoholics Anonymous). Anonymity encourages a state of privacy, and the withholding of personal details from public view in order to keep the identity of members private and to keep the principles of the programme intact.
Most members of a 12 Step fellowship have parts of their lives which could cause them harm if shared in public. Anonymity allows them the safety of recovering in a 12 Step fellowship without disclosure to a large group of people. In 12 Step fellowships, people do not use their surnames and merely interact on a first name basis for the sake of encouraging anonymity.