But Susan Freiwald, professor of law at University of San Francisco School of Law, said in a phone interview that metadata has significant privacy implications. "It's really not true that the content of our communication holds more revealing information than the metadata," she said.
In a phone interview, Jon Callas, CTO of secure communications service Silent Circle, agreed that metadata can be very revealing. "It's one of the reasons that privacy advocates have been concerned about seizure of phones and looking at call logs," he said.
In a 1996 a paper about metadata, or "communication attributes," Freiwald warned, "As it now stands, disclosure of communication attribute information presents an extremely intrusive view into people's private lives. Unfortunately, the law does little to prevent it."
Today, in 2013, metadata tells even more about us, thanks to the addition of location information, supplied by mobile phones, to say nothing about records of our online activities. Simply put, metadata can lead to criminal charges. It is thus relevant in the context of legal protections guaranteed under the U.S. Constitution.
Freiwald argues that the secrecy surrounding these surveillance programs runs contrary to what we expect from an accountable democracy. She points to the judges who oversee these programs, who are selected by the Chief Justice and who can't be contacted. They're not what we think of as a judiciary, she said.
"The criticism I've always had of surveillance programs is when they operate with the insufficient involvement of other branches, we have to rely on executive branch restraint," she said. "..These programs give too much power the the executive branch to operate in secret. The answer keeps coming back, 'don't worry, trust us.' We don't know enough and we need to know more. We need to move as much as we can of this decision making into the light."
Callas observed that when a similar program, Echelon, was revealed many years ago, there was a presumption that U.S. citizens were not the target of information gathering. He said if information about Americans is being gathered by current surveillance programs, he hopes to see some reconsideration of the laws.
Callas believes that one result of the renewed awareness of government surveillance may be that some organizations and individuals will reconsider doing business with online companies that fail to support SSL connections and take steps to secure customer data.
Callas also observes encrypted communication services have some advantages in the current environment, because they can't reveal data that has been properly encrypted. "If someone came to us with a National Security Letter, we'd hand over the zero records we have," he said.