I would have thought the opposite. If there is a false positive that leads to an arrest and ruins someone's life, but the public sees that it is a false positive, then Apple will take an enormous hit in the marketplace. Nobody will want to take on the demonstrated real risk being falsely accused of possessing CSAM.
If they have a false negative, it is unclear to me what negative effects Apple would suffer. As far as I know, nobody would know about it outside of Apple.
> Nobody will want to take on the demonstrated real risk being falsely accused of possessing CSAM.
I don't think this is much of a risk. Defamation is difficult to prove, never applies to the law enforcement agencies who are going to make these arrests and "ruin people's lives", is never going to be down to Apple anyway (Apple is only referring things for investigation). I don't think you'll see much public indignance about this--even arguing against it in the real public eye (outside of wonky venues like HN) sounds tantamount to "supporting kiddie porn" in the naïve view of most members of the public.
> If they have a false negative, it is unclear to me what negative effects Apple would suffer. As far as I know, nobody would know about it outside of Apple.
This could potentially arise in any case with an abuser or producer or enabler or pimp or Maxwell/Epstein customer who has an iPhone; which is a lot of cases. As soon as Apple devices are supposed to "detect" kiddie porn, people will ask why people like this weren't caught earlier; and since Apple has money, they won't just ask this in the court of public opinion, they will sue for damages for abuses that "should have" been prevented by Apple's inspection of their pictures. Even if that's unlikely, it's much easier for a peon whose job it is to look at kiddie porn to just forward it on; and such a case really could damage Apple's optics.
As others said, if the non-csam looks sexual at all, they'll probably get flagged for post-apple review.
Beyond that, it doesn't seem to be in apple's interest to be conservative in flagging. An employee reviewer's best interest is to minimize false negatives not false positives.
As many mentioned, even an investigation can have horrible affects on some (innocent) person's life. I would not be shocked to learn that some crafty individual working at "meme factories" creating intentional collisions with distributed images just for "fun" - and politically motivated attacks seem plausible (eg. make liberal political memes flag CSAM).
Then there are targeted motives for an attack. Have a journalist you want to attack or find a reason to warrant? Find them on dating app and send them nudes with CSAM collisions. Or any number of other targetted attacks against them.