[DaiPlusPlus]

Colossus was not a panopticon, it was operating on limited intelligence and information about the world. Now, consider a hypothetical secret and clandestine science and engineering team (think: Black Mesa East) could exist completely hidden from Colossus and fabricate a workable fission bomb, then place and detonate it somewhere as a false-flag attack that Colossus would act against.

...or even just from recent middle-eastern history: an outrageous death-cult militant faction like ISIS.

[socalgal2]

It was close enough to panopticon and was trying to increase it's reach. It was smart enough to know that not survailing everyone was a losing move. It would demand increase surveillance like it already did in the movie. Like in the movie, people might try to hide something, and like in the movie, it would notice and deal out repercussions. It would be pretty hard to form a resistance without communication or other evidence (resource movements, emissions, etc..) leaking somewhere.

[rbanffy]

Colossus didn’t have infinite intelligence, so it might be possible to hide an effort like that. Not trivial though, as it would have satellite surveillance and likely cooperation from governments who fear what it could do as a retribution. This incentive should be sufficient to make governments police violent activist groups.