One of the great rise-and-fall stories in the history of tech gadgets was the Flip camera. A pioneering, inexpensive digital video camera, the Flip became a cultural phenomenon, was bought by Cisco Systems in 2009 only to be pulled from the market two years later.

Unfortunately, the story has repeated over and over, as faddish hardware products become insanely popular, plateau, and then burn out. Just this year, fitness tracker maker Jawbone has battled investors to avoid being liquidated, smartwatch maker Pebble laid off 25% of its workforce, and wearable camera maker ION Worldwide filed for bankruptcy.

Luckily for investors, none of those companies had gone public yet. But this week public hardware makers felt the pain. On Wednesday, Fitbit slashed its outlook for holiday season sales, sending its stock down 34%. On Thursday, GoPro reported stunningly weak third quarter sales and cut its holiday quarter outlook, as well. Its shares lost almost 25% combined in regular and after hours trading.

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Each company had excuses ready, although investors weren’t assuaged. Fitbit CEO James Park told Fortune on Wednesday the company had problems producing some of its newest popular products and also blamed weak customer demand in Asia. GoPro put all the blame on production problems, saying both its newest cameras and hyped Karma drone product were hit with delays.

FitBit fit CEO Park said absent some of the hiccups this quarter, sales would have been much stronger next quarter. “The overall category still has a lot of demand and growth,” he said. “And overall our products are being well received.”

Likewise, GoPro gpro president Tony Bates said on a call with analysts that in the four weeks since the company fixed its production problems “demand is strong.”

The execs may have it right in the long run, but for now, Wall Street isn’t buying the spin. If a hardware company can’t make its new hardware without defects, investors grow alarmed.

Also not helping? The companies’ efforts to position themselves not as hardware makers vulnerable to fading fads, but as some sort of ecosystem or platform. After all, Apple aapl has grown to become the biggest company in the world on the strength of of its iPhone ecosystem. Customers don’t just buy a phone, they invest in apps and accessories and digital media—all of which becomes worthless if they defect to Android.

For more on GoPro’s new drone, watch:

Fitbit has been saying that the social aspect of its customers posting activities online and comparing performances somehow equates to a fitness platform. And on Thursday, GoPro CEO Nick Woodman described his company not as a camera maker but as “a simple end-to-end storytelling solution,” because it offered cloud-based editing software and video storage.

All those features may make the hardware products somewhat stickier, meaning customers will be more loyal. But none are so amazing and necessary as to keep the majority of customers from moving on to a competing product in the future. And what disrupts gadget makers isn’t always a competitor’s superior products, but often simply the exhaustion of the fad that they rode to popularity.

In the case of both Fitbit and GoPro, the market may have dramatically overestimated the ultimate number of people who wanted to buy the products. Until they prove otherwise, don’t expect much of a recovery.