On Monday, notorious National Security Agency whistleblower Edward Snowden was video conferenced in to a Harvard classroom to talk about his experience with the organization’s mass surveillance gathering on American citizens. One of the NSA’s worst blunders that could’ve been prevented, he mentioned, was the Boston Marathon bombings.

Snowden’s Google Hangout was part of an interview with Harvard Law Professor Lawrence Lessig, called “Institutional Corruption and the NSA.” The roughly hour-long interview touched on a number of subjects pertaining to government oversight, including mass surveillance versus targeted surveillance, for which he used the Boston Marathon bombings as a prime example.

In the video above, jump to the 40:15 mark where Snowden begins touching upon the tragic 2013 incident that killed three and injured more than 260.

Snowden argues that part of the reason Marathon bombing suspects Tamerlan and Dzhokhar Tsarnaev — the latter of which is scheduled to be in court in January 2015 for multiple charges, and faces capital punishment as a result — is that the government spends too much time and too many resources collecting data on a sweeping amount of citizens.

By conducting cyber investigations in this manner, often times undertaking pre-investigations in which intelligence on a subject is gathered based on loose associations with a specific target or event, significant violators can slip through the cracks.

“It’s not necessary to collect the communications of everyone in the country,” said Snowden. “This has been going on for more than a decade. … The question is, do we need to continue to do that when it’s not shown to have value?”

As it so happens, the Tsarnaev brothers were actually being monitored by Russian intelligence services, who even notified the FBI about them. The elder brother, Tamerlan, who died in a firefight with authorities in an early morning shootout on the streets of Watertown, was known to have Chechen militant sympathies after visiting Russia multiple times.

Despite being tipped off by Russia, the FBI only performed a cursory investigation, which Snowden attributes to limited resource constraints, even though they knew the Tsarnaevs were associated with extremism. No follow up investigation was ever made.

“I believe the reality of that is because we do have finite resources,” Snowden said. He continued:

And the question is, should we be spending $10 billion per year on mass surveillance program like the NSA to the extend that we no longer have effective means of targeted surveillance? We’re watching everybody we have no reason to be watching simply because it may have value, at the expense of being able to watch specific people for which we have a specific cause for investigating.

Though branded a traitor by some and a hero by others, the fact of the matter is Snowden’s insight and experience with the NSA affords him great authority in identifying what works and doesn’t work as far as security monitoring is concerned. In hindsight, it’s hard to argue with his case for the Marathon bombings.

An unclassified report issued by the Inspectors General in April for the Intelligence Community, Central Intelligence Agency, Department of Justice and Department of Homeland Security explicitly states, after all, “Two years before the Boston Marathon bombings, Tamerlan Tsarnaev and Zubeidat Tsarnaeva came to the attention of the Federal Bureau of Investigation (FBI) based on information received from the Russian Federal Security Service (FSB).”

Snowden currently resides in Russia where he sought and received asylum after fleeing the United States in the wake of leaking several NSA intelligence reports to the media. According to the New York Times, he is allowed to live there until 2017.