> What's the moral difference between that and checking to > see whether they also emit some electronic signal when > present? This is the key question

> What's the moral difference between that and checking to > see whether they also emit some electronic signal when > present? This is the key question actually, so I'm glad you asked it. Manually observing someone and making a note costs resources. Which means you won't bother doing it unless you have reasonable cause to. If John in accounts has a reputation for being late and not getting his work done, you might decide to have someone make a note of what time he comes in and leaves. If it's automated, that cost goes away, and you can just randomly trawl the data and look for anyone; it's become massively asymmetric. Suddenly John in accounts who was 10 minutes late every day but doing a good job gets a call from HR. This is generally the problem with mass surveillance and putting the data in to easily queried databases: the cost to query and surveil becomes much much less, which removes the need to have reasonable cause -- you can just go for fishing trips and see what you find.