The slipperly slope follows: once there is state login, it actually incentivizes big tech to converge on it, since they can converge on universal fingerprinting (even without direct legal identifying info) using metadata since it would provide a guarantee of a single person using a single login across properties.
Once the technocratic system and the state have unified on it's view of subjects... that's where the scary stuff can happen. The covid lockdown and vaccination hysteria could have been 1000x more evil under this system, which is hard to fathom.
