"bad for business" leads to systems that do unexpected things. For instance, on-device generate identifiers for any image sent, and send the identifier out-of-band. This helps catch child pornography.
I can imagine the same thing done for text. The text might be encrypted, but interest keywords might be generated on-device and sent out-of-band.
I can imagine the same thing done for text. The text might be encrypted, but interest keywords might be generated on-device and sent out-of-band.