“And if, and only if you meet a threshold of something on the order of 30 known child pornographic images matching, only then does Apple know anything about your account and know anything about those images.” More here.
Another ‘on the face to it this looks better’ announcement, but I don’t think there is a way to please everyone with this kind of scanning. Some will (quite rightly) argue that 30 is too many and that having the bar set this high makes it pointless.
Others will (quite rightly) be wary if any scanning at all no matter where the bar is. There is no right answer here…