Many people assume that unless the government actively censors, people will learn what the government has done. But most government cover-ups succeed. Daniel Ellsberg, who risked life in prison to leak the Pentagon Papers, related in his 2002 memoirs: "It is a commonplace that 'you can't keep secrets in Washington' or 'in a democracy'…. These truisms are flatly false. They are in fact cover stories, ways of flattering and misleading journalists and their readers, part of the process of keeping secrets well. The fact is that the overwhelming majority of secrets do not leak to the American public."
Cover-ups succeed because people defer to promises by government officials to investigate themselves. This was how the Nixon-era Pentagon buried scores of Vietnam atrocities even after confirming the carnage. After the My Lai controversy exploded, many U.S. soldiers reported other atrocities to the Pentagon. Nine thousand pages of documents were compiled confirming more than 300 war crimes, including seven other massacres of civilians by U.S. troops.