From The Independent's (UK) story on his arrest by US Customs on arrival in NYC on his way to DefCon, this explanation of the need for Wikileaks:
At DefCon, Mr Appelbaum refused to confirm or comment on his detention but defended Wikileaks' commitment to exposing information that governments around the world want suppressed. "All governments are on a continuum of tyranny," he said. "In the US, a cop with a gun can commit the most heinous crime and be given the benefit of the doubt. In the US, we don't have censorship but we do have collaborating news organisations."