For personal data leaking out, the rise of various far right movements comes to mind. Once a party takes total control and wants to get rid of dissidents, these data troves are even more valuable than census data was to the Nazis.

Separately, I worry about smart devices that could be used to cause electrical fires, leaks, etc at scale. Triggering many devices in a target area to do some activity that sparks even small fires allows you a decent chance of creating large fires fairly easily without a single troop hitting the ground or firing a single bullet. With the impact we saw from the Camp Fire, the government's current... issues... Etc., that's terrifying.