No. The mission of Nest is to reinvent the unloved things in your home, not to sell advertising. And Nest fundamentally believes the devices that keep them safe and comfortable should not have ads on them. You probably don’t want to hear a radio commercial come from your smoke alarm. Nest doesn't either.
The products of Nest can detect when someone’s there, and they use information like this to make our products more thoughtful. For example, the Nest Thermostat can turn itself down so you’re not heating an empty home. It also lets Nest Protect light your way at night so you don’t stub your toe.
If you want to be more literal about it, no one at Nest or Google spends the day looking at a screen tracking if you’re home or not.
Nest uses public key cryptography, HTTPS, SSL, and AES and RSA data encryption. These are all really fancy ways of saying Nest uses powerful tools to keep your data safe.
No. Nest's business is making and selling products that create a thoughtful home. Nest is not in the business of selling data. And they don’t want to be. Google does not sell Nest data either.
Nest only collects the data they believe is necessary to provide a great experience with your Nest products – to help you save energy, to help you stay safe, and to keep you in touch with your home.