Social media gets something of a bad rap for its always-on flow of information that gives everyone a voice, even if they don’t have anything of much consequence to say.

Sometimes we’re reminded of the true power Twitter, Facebook, YouTube, and the like have to capture and communicate important messages that may otherwise have been lost. Other times, we’re reminded that social media is capable of capturing events that have no place on a public forum.

Two incidents in particular from the past week help illustrate social media at its best and at its worst.

Last week, United Airlines hit the headlines over the way it forcibly removed a passenger from one of its planes after it failed to find volunteers willing to give up their seat on an overbooked a flight. A number of videos captured from the plane were shared on social media almost immediately, revealing to the world the potential horrors that await United Airlines passengers who “refuse to volunteer” to be “re-accommodated.”

On the one hand, the videos made for disturbing viewing — a grown man screaming and bloodied, yanked from a flight he’d paid for by cops at the request of a billion-dollar corporate giant. It wasn’t pleasant to watch, but it helped highlight why social media can be an immensely powerful force. Without smartphones and social media, the incident would not have garnered the global attention it subsequently received, and United Airlines would not have been forced to reconsider its procedures for managing overbooked flights. And the Chicago Police would presumably not have suspended the officers responsible.

On the flip side, as I write this, police in Cleveland, Ohio are hunting for a man who broadcast himself on Facebook Live as he killed a stranger at random. This isn’t the first time such a thing has happened, either. And the video remained online for hours after the shooting before Facebook finally removed it from the suspect’s Facebook Page.

Everyone now has a smartphone in their pocket, meaning everyone has the potential to be a journalist and a one-person film crew — recent history is awash with examples of ordinary people who have captured major events and shared them with the world.

But as United Airlines strives to overhaul its company policies and practices in the wake of damning media coverage captured by a handful of citizen hacks, the Cleveland killing has given us a stark reminder that in the wrong hands, social media really can be the darkest of forces.