To verify that that video was actually an eyewitness account, Storyful first had to find the source. It had been uploaded to a YouTube account, NekoAngel3Wolf, with no personal details, so Storyful workers searched Twitter to see who had been sharing the video. They found a user named NightNeko3, which they connected to a Pinterest account, which was linked to a Facebook account. Then they checked the name on the Facebook account against the list of marathon runners.
"We saw a person with the same [last] name who stopped her marathon run at exactly the point where that explosion was seen in the video," Clinch says.
Finally, they flipped through the phone book and called her up.
"[We] worked out that that was actually her in the video and that her daughter had uploaded that video," he says.
This type of digging is just one way Storyful vets amateur videos. Everything from the length of a shadow to a digital blemish can be used as a clue to determine whether something is actually what it claims to be. But Storyful also works with users to broker deals between people and news providers.
Jennifer Preston, a reporter for The New York Times' Lede Blog, says when the Times wants to post a video in its own player, "our practice would be to reach out to that person and to get permission and to pay them." But YouTube videos are a different story.
Viral videos can make big bucks on the Web — YouTube has a revenue-sharing system by which money from advertising is split between the uploader and the website. But as Andrew Springer, senior editor for social media at ABC News, points out, news outlets like his and the Times generally don't pay directly to embed YouTube videos.
"During the Boston bombings, when we were clearing videos and we were clearing photos that were tweeted or YouTubed or whatever, nobody came back to us and said, 'Yeah, you can use my video of the Boston bombing if you pay me X amount of dollars,' " Springer says.
There's an obvious upside to news groups being able to gather content free, but Clinch says he hopes to help change this "Wild West" attitude to what he calls a more ethical model, where people are paid for what they upload. He calls it a "win-win-win":
"The people who own the content get courtesy and part of the revenue; the platforms and the news organizations that want to use it know that they have permission to do that and also know that they can generate significant views and revenue themselves by adopting this model."
Storyful is acting as a third-party resource for mainstream news outlets around the world, but places like the BBC, Al-Jazeera and NPR have in-house teams that are doing many of the same things.
"Any news company that thinks that they can survive and thrive using only traditional news content is missing the point and is missing a huge element of what the future of news is," Clinch says.
And as the line between social and traditional media gets blurrier by the second, news organizations hope to keep the facts in focus.
Clarification Oct. 2, 2013
Previous audio and Web versions of this story could have been interpreted as suggesting that The New York Times might in some circumstances pay to embed a video from YouTube. This is not the case.