The unexpected fury of Hurricane Harvey and its chaotic aftermath in Houston have provided a microcosm of social media’s influence on the world, encapsulating both its good and bad qualities.

Social media has become one of the main means for disaster victims to ask for help, get news, updates and official instructions. It lets friends and family know that they are OK. Conversely, the hurricane triggered its own virtual storm of fake news and hoaxes – some of them genuinely dangerous.

On the plus side, when Houston’s own 911 network was overwhelmed during the most intense period of storm damage and flooding, and with power outages making it impossible to recharge phones, social media provided an alternative. It was a strictly unofficial means of alerting emergency responders and neighbors when victims were trapped in their homes or in need of help.

As noted by The Wall Street Journal, in many cases people asking for help shared their full names and physical addresses on Facebook and Twitter, enabling emergency responders to direct rescue teams to their homes through flooded neighborhoods. Some users took the additional step of tagging news organizations and journalists in order to get their requests for help noticed.

Facebook also activated its “Safety Check” feature, which alone saw 900 requests for help and 2,800 posts offering help by Monday evening, according to the WSJ.

One of the biggest informal relief efforts was mounted by the “Cajun Navy,” a group of private boat owners from Louisiana who maintain a permanent Facebook page, allowing them to spring into action over the weekend. The Cajun Navy also uses Zello, a messaging app, to communicate with storm victims and each other. 

For all that, emergency-response orgs, including the Houston Police Department and U.S. Coast Guard, are still encouraging people to call 911 or another emergency contact phone numbers. One concern is that people asking for help might turn to newer social media platforms and messaging services, which may still be unknown to officialdom.

Law enforcement and privacy experts are also worried that people asking for help are putting themselves in danger by revealing personal information that criminals may exploit later.

There has also been a huge spike in fake news and hoaxes circulating online in the wake of Harvey.

Some noteworthy, if lamentable, examples include a social-media post with a doctored photo that appears to show a shark swimming alongside a car on a flooded Houston road — which previously circulated after Hurricane Irene in 2011. Other images were real but unrelated to the hurricane. One showed a huge alligator blocking a road.

Commercial fraud and misinformation go hand in hand. Another debunked post making the rounds encourages storm victims to call a 1-800 number for emergency response — but brings them to an insurance company instead. 

Some posts appear calculated to simply cause chaos. For example, debunked tweets claiming that Houston’s water is unsafe to drink, or that residents of certain towns and neighborhoods are forbidden from returning to their homes.