Five years ago, when Google paid $3.2bn (£2.5bn) for the smart home company Nest, it felt no obligation to make any sort of pledge about what it might do with people’s data. 

Nest’s intelligent thermostats, which could monitor when people came and went from their homes and monitor energy usage, contained a potential treasure trove of personal information that Google’s advertising algorithms could, in theory, exploit for profit. 

And yet, Google declined to make any privacy commitment, merely promising to maintain Nest’s “brand identity”.

How times have changed. Last week, when Google announced a deal to pay $2.1bn for the wearable technology maker Fitbit, it went to great lengths to dispel users’…