Silliman has worked as a political organizer, a lobbyist, an ethnographer, a newspaper editor, a director of development, and as the executive editor of the Socialist Review (US). While in San Francisco, he served on numerous community boards, including the 1980 Census Oversight Committee, the Arson Task Force of the San Francisco Fire Department, and the State Department of Health's Task Force on Health Conditions in Locale Detention Facilities. Silliman worked as a market analyst in the computer industry before retiring at the end of 2011.