Snowden, appearing with the first page of the U.S. Constitution as a backdrop behind him, displayed the day-and-a-half stubble on his face seen in the familiar screen-grab photo from his first revelations in June. He spoke from an undisclosed location in Russia, with his voice and image (which occasionally froze on the screen) transmitted by seven proxy servers via the video platform Google Hangouts.
Characterized as a "call to arms" about security on the Internet, the Snowden conversation was conducted by Christopher Soghoian and Snowden's lawyer, Ben Wizner. Both are affiliated with the American Civil Liberties Union.
Snowden charged that the NSA's aggressive surveillance efforts since Sept. 11, 2001, have weakened rather than strengthened the United States, by focusing on "going on the attack to gather data, rather than focusing on Internet security, when the U.S. has so much to lose."
He also had pointed words for companies that gather information on consumers. Such companies should, he said, hold on to data only for as long as it is needed.
In response to an #AskSnowden question posed on Twitter - the talk was live-streamed on the Web, as well as in two other oversized rooms at the Austin Convention Center - the former CIA employee said that information gathered by government is more dangerous than that gathered by corporations.
"Governments have the power to deprive you of your rights," he said. "Governments can kill you, they can jail you, they can surveil you."
In an interview Sunday, Hugh Forrest, director of South by Southwest Interactive, discussed how Snowden at SXSW came to be. "As with many things, we leveraged the power of the community on this one," Forrest said. "We knew people who knew people."
"I know there's a degree of controversy about this," Forrest said. "Should you give a platform to somebody who's a fugitive and had stolen all this information? That's a worthy discussion, but not for what we're talking about at South by Southwest . . . technology and building better safeguards for privacy within technology."
On Friday, U.S. Rep. Mike Pompeo (R., Kan.), a member of the House Intelligence Committee, published an open letter to SXSW Interactive demanding that it rescind its invitation to the fugitive leaker. Pompeo said he was "deeply troubled" by the appearance of a man he called a "traitor." He said Snowden's "only apparent qualification in addressing questions of privacy is his willingness to steal from his own government and then flee to that beacon of First Amendment freedoms, the Russia of Vladimir Putin."
"I'm glad the congressman is paying so much attention to what we're doing in Austin," Forrest said. He said he hoped that "next year the NSA can come down here and talk about their perspective on this. Healthy debate is a good thing."
Early on, conversation focused on nuts and bolts of security, and Snowden's speech was often robotic-sounding and garbled. As discussion opened up to questions, though, the talk got livelier and more impassioned.
The first Internet query came from Tim Berners-Lee, inventor of the World Wide Web. He thanked Snowden and asked what he would do to improve security if he were starting the Web from scratch.
Snowden said, "We have an oversight model that can work. The problem is that the overseers are not interested in oversight. We need civil-rights champions and trusted public figures. We need a watchdog that watches Congress.
"If data is being clandestinely acquired and the public doesn't know about it, that's a problem," he said. "When national interest is distinguished from public interest, we risk losing control of representative democracy."
Asked what normal people should do to protect information on their computers, Snowden recommended full disk encryption and network encryption, and he also suggested using Web security tools such as Tor or Ghostery.
SXSW also presented "A Conversation with Julian Assange" on Saturday, with the WikiLeaks founder speaking via Skype from the Ecuadorian Embassy in London.
Internet privacy in the post-Snowden era has been a big topic so far in this year's Interactive conference, with privacy anxiety much in evidence in many of the panel discussions. Forrest said Interactive would draw slightly more than last year's 30,000 registrants from more than 50 countries.
Snowden said he was spurred into action because "I saw the Constitution was being violated on a massive scale. The meaning of 'unreasonable search and seizure,' changed to 'any seizure is fine, just don't search it.' " He expressed skepticism that governments gathering data can be trusted to handle it properly: "What I wanted to do was inform the public so that they could make an informed decision about what to do."
"Every society has benefited from the leaks," he argued. "The world is a more secure place. Would I do it again? Absolutely."