There is something similar to this: `Spotify granted patent to use mic to infer emotional state, age, gender, and accent`[0]. Not surprising, given how data hungry most tech companies are now. Without data, they are dead. But how much is really needed to serve ADs? Do we really need to be doing creepy things like 'sentiment analysis' or peering inside the brain? How much access is too much access? I think we are slowly learning the threshold piece by piece.
We arnt slowly learning the threshold. It's known, and we passed it a long time ago. People turn off tracking when given the choice and told what is being tracked already. Much less some future peering inside the brain.
[0] https://www.privateinternetaccess.com/blog/spotify-granted-p...