Welcome to MIT Technology Review’s second annual list of top tech flops. Without further preamble, here are the technologies we thought did the least for humanity in 2015.

Hoverboards 

It was the hot 2015 gift item that went up in flames. Literally. Hoverboards, the two-wheeled, self-balancing scooters, are like Segways without the handle, packed with a circuit board and two AC motors inside the wheels. A rider balances thanks to a phenomenon called the “inverted pendulum.” The problem: shoddy lithium-ion batteries in some hoverboards have caught fire. As quickly as the fad took off, popular hoverboards were pulled by Amazon and banned by airlines as a threat. The U.S. Consumer Product Safety Commission said in December that it is “actively investigating hoverboard-related fires across the country,” as well as dozens of reports from ERs of “concussions, fractures, contusions/abrasions, and internal organ injuries.”

More: “Why Hoverboards Keep Exploding” in Wired

Theranos’s nanotainers

Theranos set out to disrupt diagnostics with cheap tests that need only a few drops of blood—a finger prick, not the usual needle draw. By collecting blood in “nanotainers,” Theranos said, it could accurately run 200 laboratory tests on tiny volumes of blood. Investors piled in, valuing the startup at an eye-popping $9 billion.

A technology able to do that really would be worth billions. But there is little evidence that Theranos ever invented one. After facing questions about the accuracy of its tests, this year Theranos withdrew its nanotainers from the market. It currently uses conventional blood draws for all its testing, the company says.

More: “Hot Startup Theranos Has Struggled” in the Wall Street Journal
“Can Elizabeth Holmes Save Her Unicorn?”in Bloomberg BusinessWeek

Coal power

Burning rocks to make electricity is a technology straight out of the early 20th century. So perhaps it’s no wonder that coal had its worst year ever in 2015, under pressure from clean-air rules and cheap natural gas. The amount of electricity generated from coal in the United States fell by 12 percent through September. And that’s nothing compared with the tumble taken by coal outfits like Peabody Energy, whose stock price has dropped from $1,000 to $8 a share over the last four years.

But don’t think coal is some laughable anachronism like buggy whips. It’s an existential threat. That’s because burning it pumps twice as much carbon into the atmosphere as burning natural gas. Emissions from developing countries such India, which gets 70 percent of its electrical power from coal and needs much more electricity, could cause catastrophic climate change regardless of whether wealthier nations move to cleaner options.

More: “India’s Energy Crisis” in MIT Technology Review

Gene-edited human embryos

In April, Chinese scientists published a report disclosing that they had changed the DNA of human embryos using the gene-editing method CRISPR. Although the embryos never left the lab, the paper quickly ignited a debate over the possibility of designer humans. Whether you fear or applaud the idea of babies with made-to-order genes, one problem with the experiment in China was just how little scientific knowledge was gained by opening this Pandora’s box. All the results were easily predicted from previous experiments on animal embryos.

Some Western academic leaders have tried to rehabilitate the Chinese work, calling it “good science” with a “cautionary message.” But a different argument is that it was a callous, slapdash effort to score a sloppy first. And now that genetically modified humans are really possible, that’s precisely the sort of behavior we should all be worried about. Let’s not do a rush job on the species, folks.

More: “Scientists on Gene-Edited Babies: It’s “Irresponsible” for Now” in MIT Technology Review.
“Engineering the Perfect Baby” in MIT Technology Review

Yahoo

Okay, I know, Yahoo is a company, not a technology. And maybe that’s its problem. The company pioneered the idea of an “Internet portal” and still operates the third-most-visited property on the Web (after Google and Facebook). But Yahoo can’t seem to grow any more. Instead, newer services like messaging apps keep cutting into its audience. Investors this year clamored for fixes. Fire CEO Marissa Mayer! Sell off the search engine! End free cafeteria lunches! The bigger problem is that Yahoo is still a “desktop” company in a mobile age. Only 20 percent of its advertising revenue comes from mobile devices, compared with 74 percent for Facebook.

More: “Diagnosing Yahoo’s Ills” in the New York Times
“Mobile to Account for More than Half of Digital Ad Spending” by eMarketer

Bulk collection of phone records

The program to secretly collect and store all Americans’ phone records—the existence of which the National Security Agency denied for years—finally ended in November. The data, about who called whom from any phone, amounted to electronic surveillance of Americans (as well as citizens of other countries) regardless of whether they were suspected of any crime.

The program propelled technical innovations inside the government: grabbing and storing so much data wasn’t easy. But it was flatly illegal, according to a May U.S. appeals court ruling, which said that laws should have “never been interpreted to authorize anything approaching the breadth of the sweeping surveillance at issue here.”

There’s no evidence the system was abused—but also very little that it was useful in stopping terrorist threats. Congress passed a new law in 2015 that requires the NSA to get a court order and show a “reasonable” suspicion of terrorist activity before delving into a person’s call history.

More: “NSA Ends Sept. 11-Era Surveillance Program” by NPR
“Why the New NSA Restrictions Won’t Harm National Security” in MIT Technology Review