Google next big idea is to embed the core functionality of a smartphone into a pair of glasses - complete with a camera, web browsing and voice recognition.
But while most people in the tech world can't wait to get their hands on a pair, a few voices are starting to raise concerns about the potential downsides.
One of these is obvious - they're expensive and they look, well, nerdy.
But another is more insidious - the potentially devastating effect on privacy if everyone is suddenly wearing inscrutable cameras coupled with an ability to detect identities, upload to the web and even - theoretically - publish without consent.
The darker vision of Google Glass has been described in a blog post by Mark Hurst, founder of Creative Good and a former InfoWorld 'Netrepreneur of the Year'.
In his article he writes that "the key experiential question of Google Glass isn't what it's like to wear them, it's what it's like to be around someone else who's wearing them".
Hurst imagines a bus ride in which just one passenger is wearing Google Glass, but in which the audio, video and identities of everyone on board could be recorded, uploaded, tagged and published to Google's servers.
"First, take the video feeds from every Google Glass headset, worn by users worldwide... Now add in facial recognition and the identity database that Google is building within Google Plus...
Finally, consider the speech-to-text software that Google already employs... Any audio in a video could, technically speaking, be converted to text..
Anything you say within earshot could be recorded, associated with the text, and tagged to your online identity. And stored in Google's search index. Permanently.
The issue, he continues, is that the Google Glass user might not even have to request that videos be recorded and stored before they are uploaded to the cloud.
"Starting today, anywhere you go within range of a Google Glass device, everything you do could be recorded and uploaded to Google's cloud, and stored there for the rest of your life," he said.
"You won't know if you're being recorded or not; and even if you do, you'll have no way to stop it."
Meanwhile other tech writers who have used Google Glass have reported a mixed experience. For Joshua Topolsky, editor in chief of The Verge, the rise of Glass is not if "but when".
"I walked away convinced that this wasn't just one of Google's weird flights of fancy," he said after a recent test.
"The more I used Glass the more it made sense to me; the more I wanted it. If the team had told me I could sign up to have my current glasses augmented with Glass technology, I would have put pen to paper (and money in their hands) right then and there."
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