China is an "excellent" example of the surveillance and thought police state that people in the west fear is just around the corner. China is already there. They're going all out with tracking people and punishing them for not doing the "right" thing. There's cameras with facial recognition all over the place, police are wearing glasses with facial recognition systems built in and the social credit system is already up and running in some places. All kinds of databases are being connected, so doing something stupid, like getting a parking ticket, will have knock-on effects on all kinds of other things, like not being able to buy a train ticket or using certain services.
The scary part is that it might just work. If they get it fully up and running as intended the end result will be an automated system of self-policing. People who oppose the government will be marginalized, as other people start avoiding them because the system will lower their score just for associating with them, and if the system is tuned just right it will all happen automatically. Dissent will be crushed before it even becomes an issue.
And of course, if it is seen to work it will be very tempting for other countries to start implementing similar systems, starting with the more "benign" functionality, then slowly expanding it, one function at a time. Some US cities already have facial recognition camera systems up and running (thanks, Jeff Bezos), and London is riddled with CCTV cameras.
When they start connecting all the disparate systems you will end up with what you might call an emergent surveillance state. In China it will be in the name of social harmony, in the west it will be in the name of ad revenue, but the results might be very similar.
I read a short story recently by Rudy Rucker in Asimov's Sci Fi zine March/April 2018 called "Emojis" that expands on this but in a pretty benign and funny way. Here's a quote from someone who reviewed it:
It’s about how technology will change our social interactions. In this story, a man programs a nano-virus that infects a person connects to the internet and then overlays emojis over reality so the user can understand what they are thinking and feeling. It’s called the empathy bug. They call it a bug because it’s contagious, as the programmer finds out when he goes home and makes love to his wife only to find out she has caught his empathy bug. This raises a bunch of ethical questions–
I can see this being introduced in the US just like an extension of your social networks, only like totally more awesome! People would eat it up. They'd walk around with emojis above their heads that could not only be hacked into by government/police for "security reasons" but to set someone up with an ISIS or Illegal Immigrant or hell, Socialist emoji to get the public to respond accordingly.
Okay, maybe that won't have a chance to happen before the doomsday device goes off but we're always closer to the outlandish scifi stories than we think.