If the Arab Spring realized social media’s civic promise, then the Boston bombings may be the moment that promise evaporated.

A man types on a computer keyboard in Warsaw in this February 28, 2013 illustration file picture.

By now, we’re only too familiar with the much-analyzed, much-disparaged mistakes the ambiguous “hivemind” made in the wake of the attacks. It began with Reddit’s now-infamous investigative efforts, which attracted record audiences to the site while terrorizing an innocent 17-year-old and the family of a missing Brown student. Behind that high-profile calamity, in the corners of Reddit usually left to perverts and masochists, users traded carnage-filled photos from the crime scene, theorizing on the causes of death.

Twitter users live-tweeted the Boston police scanner like an episode of HBO’s “Homeland.” Interested parties — including reporters — ripped into the Facebook and Youtube profiles of the suspects, eager for autopsies and “insights.”

In a thousand disparate ways, across every available social channel, we all made the same mistake: We believed we were entitled to and could easily possess first-hand knowledge of the Boston tragedy. And we believed our networks, the ones we had come to know and trust, imparted that knowledge.

After all, social networks promise to democratize information — to condense distances, bypass gatekeepers and distribute all available knowledge to the virtual commune, so that everyone can see what only one or a few could have seen before.

The problem, of course, is that the Internet is not the master key able to unlock all knowledge. And to further complicate things, the slices of life seen online — the iPhone photo or the police scanner tweet — rarely make up enough to say anything meaningful or even accurate about the full picture.

That networked “knowledge” you pull down from the digital ether is often dehydrated information, condensed to fit a tweet. Digital lives, Matt Buchanan wrote in an essay on the Tsarnaevs, “are divorced from their original circumstances, reconstituted in a world brimming with new context.”

That’s true not only of people, of course, but also of crime scenes and police chases. Like a digital update to Plato’s cave, social media users looked at photos, scanner transcripts and Amazon wish lists — online representations of real-life things — and easily convinced themselves that they knew something, that they saw the thing itself. Without realizing it, in many cases, they transubstantiated Internet rumor into real-life truth. 

Can we attribute that switch to ignorance or curiosity? On Reddit, at least, it doesn’t seem so. In the forums where users ripped apart the /r/findbostonbombers “investigation,” criticizing moderators and asking for an “anti-witchhunt” button, commenters blamed arrogance and ego and self-aggrandizement.

Any reasonable person would know, they argued, that looking at photos of the bombing scene would not equip some self-styled detective to judge “suspects” and diagnose victims as if he stood, as a fully-trained law enforcement official, on Boylston St. and watched the bombs explode. No reasonable person could really read Dzhokhar’s Twitter feed and convince herself that she knew him — or that, as some teenagers have deluded themselves, that his “normal” tweets evidence his innocence.

But on Twitter and Reddit, in the media and on Broadcastify, that’s exactly what people did. Chalk it up to the cognitive gap between the virtual and the physical, if you will. The fact remains that — in the wake of a devastating tragedy, at a moment that should have humbled us — the only thread uniting social media users was our conviction of the Internet’s infallibility.