In the way Nest allowed your thermostat to connect to your smart phone, the web of things has become a generally accepted technology. When considering how devices actually connect to one another, the privacy implications are the achilles heel, especially when thinking at a Google-scale. Google had created a new technology, called "Nearby", that allowed mobile devices to detect one another within a 30 foot radius. All of our early user-testing indicated that the real challenge was user comprehension, and trust, that their privacy was in no way affected by this.
Note: All of the illustrations shown were created by Fuzzco. I was the lead UX designer, UI designer, and art director for the work below. You can read more about Google's Nearby feature: here, and discover how it's being used for Chromecast: here.
The largest hurdle for users in understanding this technology was the use of their microphone. Of course, they had never been introduced to the concept of pairing devices by way of ultra-high-frequency sound. They were understandably confused about why Google needed a snippit of sound from them in order to accomplish a simple task, like sharing a photo.
So we made it simple, by allowing the user to "test" the functionality during on-boarding. They could press a button and literally nothing would happen. 100% of users then understood that the speakers and microphone were being used simply to help the devices find each other.