The device itself is just a "gateway" to the google services that it connects to, via the app on your phone or tablet, or through any other method of logging into your google account you may have used. There is no real data that is stored on the device itself, so it's just as safe as using your smartphone or any other device that can access your google account. I personally place a fair amount of trust in Google and I'm not really worried about improper use of my information via their services. As far as "listening in" to your live interactions between the device and yourself is highly unlikely. First they'd have to have access to your private home network (which if you've set everything up properly and have everything secured with strong passwords) that shouldn't be an issue. Second they'd have also tap into the bluetooth connection between the speaker and your other device. A lot of work to listen to you ask about the weather and find out what Trump's latest tweet is. The speaker button on the back might be to sync multiple speakers in the household for multi room simultaneous streaming. I could be wrong though, I didn't feel like pulling out the manual either to see what it does, since I currently only own one.