This is a step further, but say we could interface directly with auditory areas to have access to a massive internal library of different sounds. You could play songs on demand, verbatim recall anything that was said to you in the past, etc.
Sounds pretty dope at first, but this kind of thing would likely be developed before future researchers fully understand the entire human brain. So that means they would not really understand how the brain would interface with it, especially across long time scales and a heterogeneous population.
Forget any sort of malicious action, and still God only knows the potential side effects. It could massively fuck with ability to learn over time, cause terrible rumination issues, maybe it could trigger psychosis in high risk individuals, maybe it would fuck up your dreams.
Like seriously, for anybody that is trying to cut back phone usage, just imagine if you could check your feed purely by thinking about it. How freaking hard would it be to control yourself then? And that is an obvious immediate consequence type thing, not a deep consideration of potential problems.
Anyway, this mostly reminded me of that Black Mirror episode about the parent watching the kid via a brain implant, which I thought was too heavy handed. There are a ton of ways brain implants could be scary without using the super obvious surveillance angle. Honestly just the "blurring out of bad things" feature would have made for a cooler episode IMO.