Amazon says the internet-sharing network helps connected devices stay online, but there are concerns about privacy and surveillance.
A move by Amazon to enroll U.S. users of Alexa, Echo and other popular gadgets into sharing their home internet with neighbours has alarmed privacy experts who fear the scheme might open Americans to hackers, stalkers and other security breaches.
As of Tuesday, anyone in the United States who owns a newer model of Amazon's many popular devices - be it the Alexa voice assistant, the Ring camera or Echo speaker - was automatically enrolled in the network unless they had actively opted out.
Called Sidewalk, the network enables users to share a small portion of their internet bandwidth which is then pooled together to create a so-called mesh network.
Amazon has said the network "extends the working range of low-bandwidth devices, and helps devices stay online, even if they are outside the range of the user's home wifi."
It can "even locate pets or lost items".
But some security and privacy experts are worried.
"It is very concerning that Sidewalk will be automatically turned on for millions of Amazon device owners. Many people will not understand what it means," said Eric Null, U.S. policy manager at Access Now, a digital rights group.
"Very few people - only those technically savvy - will understand the risks associated with allowing anyone's Amazon devices to use part of their home network," he added.
Consumer electronics that collect and share data are more common now, with the coronavirus pandemic increasing the use of gadgets in an average U.S. household to 25 internet-connected devices from 11 in 2019, according to consulting firm Deloitte.
Amazon has been criticised for products that facilitate surveillance and profiling, and last week said it planned to be more transparent about police requests for users' video footage through its neighbourhood watch app, Ring Neighbors.
Amazon has said it has "carefully designed privacy protections into how Sidewalk collects, stores, and uses metadata," and that the network protects customer privacy "by limiting the amount and type of metadata that Amazon needs."
Once on Sidewalk, Amazon gadgets could work without interruption even outside the home. But that could also make the networks vulnerable to hacking and misuse, while also giving Amazon more data on how we shop, live, work and play.
The company has not explained how it plans to prevent the Sidewalk network from infiltrating home networks, and "it's only a matter of time before someone's network gets hacked and data gets breached," Null told the Thomson Reuters Foundation.
In ensuring that its devices never lose connection, the Amazon devices "that contribute to mass surveillance that can be abused by local law enforcement, such as Ring, will only get more abused as they will essentially never turn off," he added.
Social apps focused on neighbourhood safety have come under scrutiny in recent months, with the crime-tracking app Citizen criticised for offering a $30,000 reward for a man it wrongly said was an arson suspect.
The company has since said it regrets the mistake.
Hyper-local site Nextdoor has also been slammed for racial profiling and misinformation on its site.
The site has said it is adding user prompts and moderator training to mitigate these issues.
Technology experts have also raised privacy and surveillance concerns with Amazon Tile, a tiny Bluetooth device that can be attached to pets, keys and wallets and tracked via an app.
Tile joins the Sidewalk network on June 14.
"Our concern with Sidewalk is how it can be used in places where it can enable stalking - like with the Tile trackers," said Jon Callas, director of technology projects at Electronic Frontier Foundation, a digital rights non-profit.
"The protocols themselves have a good characteristic. But the biggest issue is if you can find your keys, you can find a person," he said.
"Sidewalk per se is a wireless network for automation - in that aspect it seems to be both secure and private. The question is thus not what it is, but how people can use and abuse it."
(Reporting by Rina Chandran @rinachandran; Editing by Lyndsay Griffiths. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers the lives of people around the world who struggle to live freely or fairly. Visit http://news.trust.org)